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

The fill-in tackle on the right side, Joshua Ezeudu, allowed a team-high five pressures. — Sam McDowell, Kansas City Star, 26 Oct. 2026

In an interview with People published on October 23, Ashley discussed being employed in the family’s Wernersville, Pennsylvania home as a cleaner and fill-in nanny. — Hannah Malach, InStyle, 23 Oct. 2026

Verb

And Loftin held his own at third after filling in for 2025 Gold Glover Maikel Garcia. — Jaylon Thompson, Kansas City Star, 2 Nov. 2026

Grohl gave up his position on the main kit and left the stage so that it could be taken over by John Douglas, the drum tech who had come to fill in previously for Kramer. — Chris Willman, Variety, 30 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