cap

1 of 8

noun (1)

ˈkap 

often attributive

1

a

: a head covering especially with a visor and no brim

b

: a distinctive head covering emblematic of a position or office: such as

(1)

: a cardinal's biretta

(2)

: mortarboard

2

: a natural cover or top: such as

a

: an overlying rock layer that is usually hard to penetrate

b(1)

: pileus

(2)

: calyptra

c

: the top of a bird's head or a patch of distinctively colored feathers in this area

3

a

: something that serves as a cover or protection especially for a tip, knob, or end

a bottle cap

b

: a fitting for closing the end of a tube

c

British : cervical cap

d

: an artificial crown for a tooth

4

: an overlaying or covering structure

5

: a paper or metal container holding an explosive charge (as for a toy pistol)

6

: an upper limit (as on expenditures) : ceiling

a cap on military spending

7

: the symbol ∩ indicating the intersection of two sets compare cup sense 9

8

: a cluster of molecules or chemical groups bound to one end or a region of a cell, virus, or molecule

see also:

cap in hand

cap

2 of 8

verb (1)

capped; capping

transitive verb

1

a

: to provide or protect with a cap

cap a bottle

b

: to give a cap to as a symbol of honor, rank, or achievement

2

: to form a cap over : crown

mountains capped with mist

3

a

: to follow with something more noticeable or more significant : outdo

b

: to bring to a climax or conclusion

cap off the show with a song

4

: to form a chemical cap on

5

: to prevent from growing or spreading : set an upper limit on

cap oil prices

6

: to supply (a tooth) with an artificial crown

intransitive verb

: to form or produce a chemical cap

cap

3 of 8

noun (2)

: a small amount of an illegal or legally regulated drug

especially : a small amount of a drug enclosed in a capsule

a cap of cocaine

cap

4 of 8

noun (3)

plural caps

1

: capitalization sense 1d

2

: a capital letter

—usually plural

a message written in caps

According to [linguist Deborah] Tannen, women's preference for expressive hashtags is "similar to their using exclamation points, caps, and repetition of letters to show emphasis, and to the fact that women's spoken intonation patterns tend to vary more than men's."

—Jessica Bennett

Good netiquette includes not using all caps [=exclusively capital letters] when typing, as it comes across as shouting.

—John DeGarmo

cap

5 of 8

verb (2)

capped; capping or cappin' ˈka-pən 

intransitive verb

1

African American English slang : to make an untrue statement with intent to deceive : lie

Worst thing you could do is cap to me

—@_d157, on X, formerly Twitter

Everybody's like, "Oh you're lying, you cappin'."

—De'Aaron Fox, quoted at The Ringer

They cappin' to you. None of it's name brand. It's all a lie.

—Kurt Hammer, quoted at Newsweek (online)

often, specifically : to lie by boasting or exaggerating

We will get them for sure … not even in doubt or capping …

—@damianfx_, on X, formerly Twitter

2

African American English slang : to engage in a ritualized exchange of insults with someone : to tease or insult a person in capping

—usually used with on

As a member a fraternity, I can joke around and cap on a fellow fraternity brother.

—Roland S. Martin

When capping on someone, the top insults are the ones directed at a person's mother.

—Allan Johnson

cap

6 of 8

noun (4)

slang

: nonsense

… a good point even tho that last part is cap.

—@gamecubep, on X, formerly Twitter

especially : empty boasting or dishonest talk

—often used in the phrase to call cap (on)

… some continue to call cap on … claims that he was working on a joint album with the late B.I.G. …

—Sha Be Allah

see also no cap

Note: Usage of this term originated in African American English and has since become widespread.

cap

7 of 8

abbreviation (1)

1

capacity

2

capital

3

capitalize; capitalized

CAP

8 of 8

abbreviation (2)

1

Civil Air Patrol

2

combat air patrol

Synonyms of cap

Noun (1)

• hat
• helmet

Verb (1)

• limit
• restrict

Noun (2)

• pill
• tablet
• capsule

Examples of cap in a Sentence

Noun (1)

grabbed a cap and plopped it on his head before running out

I can't find the cap to the milk bottle

a cap on player salary expenditures was suggested as a way to keep small market teams competitive

Verb (1)

a pipe capped at one end

Be sure to cap the pen when you are done using it.

The report caps a ten-year study of lung cancer among nonsmokers.

a concert capped by a fantastic fireworks display

If the teams don't cap player salaries, the league won't survive.

The law would cap legal immigration.

The government wants to cap councils that spend too much.

Noun (2)

I prefer to take my medicine as caps rather than in liquid form

Recent Examples on the Web

Noun

As of Monday morning, the Cowboys are over $56 million over the league’s salary cap for 2026 with free agency set to begin in less than 10 days. —Nick Harris, Fort Worth Star-Telegram, 2 Mar. 2026

That would save the Dolphins $11 million against the 2026 cap. —Barry Jackson, Miami Herald, 1 Mar. 2026

Verb

Kavan’s no-hitter capped an impressive weekend in the circle for Texas. —Thomas Jones, Austin American Statesman, 2 Mar. 2026

The win came on the heels of the worst month in the Bulls’ franchise history, a winless February that capped off an 11-game losing streak. —Julia Poe, Chicago Tribune, 2 Mar. 2026

Word History

Etymology

Noun (1) and Verb (1)

Middle English cappe, from Old English cæppe, from Late Latin cappa head covering, cloak

Noun (2)

short for capsule

Verb (2)

perhaps development of cap entry 2 in sense "outdo, surpass"

Noun (4)

derivative of cap entry 5

First Known Use

Noun (1)

before the 12th century, in the meaning defined at sense 1a

Verb (1)

15th century, in the meaning defined at transitive sense 1a

Noun (2)

1942, in the meaning defined above

Noun (3)

1906, in the meaning defined at sense 1

Verb (2)

1906, in the meaning defined at sense 1

Noun (4)

2011, in the meaning defined above

Phrases Containing cap

• a feather in one's cap
• a feather in someone's cap
• baseball cap
• bathing cap
• blasting cap
• cap-and-trade
• cap-a-pie
• cap in hand
• cap sleeve
• cervical cap
• cradle cap
• death cap
• doff one's cap to
• dunce cap
• fool's cap
• garrison cap
• gimme cap
• ice cap
• if the cap fits
• if the cap fits, wear it
• inky cap
• liberty cap
• mushroom cap
• newsboy cap
• no cap
• overseas cap
• percussion cap
• put one's thinking cap on
• put on one's thinking cap
• root cap
• screw cap/top
• service cap
• shower/bathing cap
• shower cap
• stocking cap
• swimming cap
• thinking cap
• tip one's cap/hat
• to call cap (on)
• to cap it off
• toe cap
• trucker cap
• watch cap

Rhymes for cap

• app
• chap
• clap
• crap
• flap
• frap
• gap
• hap
• lap
• nap
• nappe
• pap

Kids Definition

cap

1 of 2 noun

ˈkap 

1

: a head covering

especially : one that has a visor and no brim

2

: something that serves as a cover or protection for something

a bottle cap

3

: a natural cover or top: as

a

: the umbrella-shaped part that bears the spores of a mushroom

b

: the top of a bird's head

4

: a paper or metal container holding a small explosive charge (as for a toy pistol)

cap

2 of 2 verb

capped; capping

1

: to cover or provide with a cap

2

: to follow with something : outdo

3

: to bring to a conclusion

capped off the show with a song

4

: to prevent from growing or spreading : set a limit on

capped oil prices

Etymology

Noun

Middle English cappe "cap," from Old English cæppe "cap," from Latin cappa "head covering, cloak" — related to cape entry 2, chapel

Medical Definition

cap

1 of 3 noun

ˈkap 

often attributive

1

: a natural cover or top: as

a

: pileus

b

: patella, kneecap

2

: something that serves as a cover or protection especially for a tip, knob, or end (as of a tooth)

3

British : cervical cap

4

: a cluster of molecules or chemical groups bound to one end or a region of a cell, virus, or molecule

the cell surface receptors were redistributed into caps

cap

2 of 3 verb

capped; capping

transitive verb

1

: to invest (a student nurse) with a cap as an indication of completion of a probationary period of study

2

: to cover (a diseased or exposed part of a tooth) with a protective substance

3

: to form a chemical cap on

the capped end of a messenger RNA

intransitive verb

: to form or produce a chemical cap

cap

3 of 3 abbreviation

1

capacity

2

capsule

Legal Definition

cap

noun

ˈkap 

: an upper limit

a jury found that KAL had committed “willful misconduct,” thus removing the Warsaw Convention's $75,000 cap on damages

—Dooley v. Korean Air Lines, 524 U.S. 116 (1998)

cap verb