Definition of key
(Entry 1 of 7)
1a
: a usually metal instrument by which the bolt of a lock is turned
b
: any of various devices having the form or function of such a key
a key for winding a clock
2a
: a means of gaining or preventing entrance, possession, or control
b
: an instrumental or deciding factor
the key to her success
3a
: something that gives an explanation or identification or provides a solution
the key to a riddle
b
: a list of words or phrases giving an explanation of symbols or abbreviations
a pronunciation key in a dictionary
c
: an aid to interpretation or identification : clue
a key to understanding their motivation
e
: a map legend
4a
: a part to be depressed by a finger that serves as one unit of a keyboard
also
: a representation of such a key (such as a space delineated on a touch screen)
Tiny keys on your iPhone's screen can be difficult to hit accurately. — Cherlynn Low
b
: one of the levers of a keyboard musical instrument that actuates the mechanism and produces the tones
c
: a lever that controls a vent in the side of a woodwind instrument or a valve in a brass instrument
5
: a system of tones and harmonies generated from a hierarchical scale of seven tones based on a tonic
the key of G major
6a
: characteristic style or tone
b
: the tone or pitch of a voice
c
: the predominant tone of a photograph with respect to its lightness or darkness
7
: a decoration or charm resembling a key
8
: a small switch for opening or closing an electric circuit
a telegraph key
9
: the set of instructions governing the encipherment and decipherment of messages
an encryption key
10
: a free-throw area in basketball : free throw lane
a jump shot from the top of the key
11a(1)
: cotter pin
(2)
: cotter
b
: a keystone in an arch
c
: a small piece of wood or metal used as a wedge or for preventing motion between parts
12
: samara
key
adjectiveDefinition of key (Entry 2 of 7)
: extremely or crucially important
key issues a key moment in the game a key member of the staff
key
verb
keyed; keying; keys
Definition of key (Entry 3 of 7)
1
: to lock or secure with or as if with a key : fasten: such as
a
: to secure (something, as a pulley on a shaft) by a key
b
: to finish off (an arch) by inserting a keystone
2
: to regulate the musical pitch of
key the strings
3
: to bring into harmony or conformity : make appropriate : attune
remarks keyed to a situation
4
: to identify (a biological specimen) by a key (see key entry 1 sense 3d)
5
: to provide with identifying or explanatory cross-references
instructions keyed to accompanying drawings— John Gartner
6
: to make nervous, tense, or excited
—usually used with up was too keyed up to sleep
7
: to enter or input (text or data) by using a keyboard
keying changes to a manuscript
—often used with in or into key in a passwordinformation being keyed into a database
8
: to be essential to : play the most important part in
defense keyed the victory
9
: to vandalize by scratching with a key
someone keyed my car door
1
: to use a key
2
: to observe the position or movement of an opposing player in football in order to anticipate the play
—usually used with on The middle linebacker was keying on the halfback.
3
: to operate a machine by means of a keyboard : keyboard
key
noun (2)Definition of key (Entry 4 of 7)
: a low island or reef
specifically
: any of the coral islets off the southern coast of Florida
the Florida Keys
key
noun (3)Definition of key (Entry 5 of 7)
slang
: a kilogram especially of marijuana or heroin
Key
biographical name (1)Definition of Key (Entry 6 of 7)
Francis Scott 1779–1843 American lawyer and author of "The Star-Spangled Banner"
Key
biographical name (2)Definition of Key (Entry 7 of 7)
John (Phillip) 1961– prime minister of New Zealand (2008–16)
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
February 2021 Words of the Day Quiz
-
- Which is a synonym of perdure?

Test your visual vocabulary with our 10-question challenge!
TAKE THE QUIZ
Spell words. Make bears.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Words at Play
Ask the Editors
Share key
Time Traveler for key
The first known use of key was before the 12th century
See more words from the same century