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

Jones has been solid as the fill-in QB for Purdy, leading the 49ers to a 5-2 record as a starter. —Matt Audilet, MSNBC Newsweek, 8 Nov. 2025

Jennings was brought off the practice squad as a fill-in. —Doug Kyed, Boston Herald, 7 Nov. 2025

Verb

Built with a black premium leather upper, each of the shoe’s signature perforation holes are filled in with metal studs which are dotted on the toe box and heel and appear in star shapes beneath the medial and lateral Swoosh logos. —Riley Jones, Footwear News, 13 Nov. 2025

Broadway star Lin-Manuel Miranda filled in for Van Der Beek, who made a virtual appearance instead. —Lisa Respers France, CNN Money, 13 Nov. 2025

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
• deerskin
• foreskin
• fuchsin
• herein
• kingpin
• linchpin
• pigskin
• pinyin

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