fill-in

1 of 2

noun

ˈfil-ˌin 

: someone or something that fills in

She performed well as the emergency fill-in.

fill in

2 of 2

verb

filled in; filling in; fills in

transitive verb

1

: to enrich (something, such as a design) with detail

2

: to give necessary or recently acquired information to

I'll fill you in

intransitive verb

: to fill a vacancy usually temporarily

Interns filled in for regular staffers.

Synonyms of fill-in

Noun

• substitute
• replacement
• backup

Verb

• inform
• tell
• advise
• catch up

Examples of fill-in in a Sentence

Noun

I'm just a fill-in, so I have no idea where office supplies are kept

Verb

my friend quickly filled me in on the portion of the movie that I had missed

she's only filling in while the regular secretary is on vacation

Recent Examples on the Web

Noun

Soderbergh is a fascinating name to work in a fill-in capacity, let alone on a tentpole superhero film. — Brian Welk, IndieWire, 15 Oct. 2026

Huntley completed 24 of 32 passes for 201 yards and two touchdowns as the fill-in starter for Lamar Jackson, who has an ankle injury and cheered from the sideline in street clothes. — ABC News, 12 Oct. 2026

Verb

Kevin Korchinski, Chicago’s top pick in the 2022 draft, seventh overall, filled in and played his second game this season. — ABC News, 25 Oct. 2026

With Kahlil Benson continuing to fill in for Josh Simmons at left tackle, Joshua Ezeudu made the start at right tackle in place of Jaylon Moore, who was ruled out because of a concussion. — Kansas City Star, 25 Oct. 2026

Word History

First Known Use

Noun

1917, in the meaning defined above

Verb

1840, in the meaning defined at transitive sense 1

Rhymes for fill-in

• akin
• auxin
• buckskin
• chagrin
• crankpin
• deerskin
• foreskin
• fuchsin
• herein
• kingpin
• linchpin
• pigskin

Kids Definition

fill in

verb

1

: to furnish with specified information

fill in an application

filled us in on the latest news

2

: to fill a vacancy usually temporarily : substitute

filled in during the emergency