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 starting right guard was in the midst of his most impressive stretch as a pro when his right Achilles ruptured in the Panthers’ blowout loss. — Charlotte Observer, 7 July 2026

Ski, who previously worked at V-103 from 1998 to 2012 and from 2018 to 2020, rejoined the station in May as a weekend and fill-in host. — Rodney Ho, AJC.com, 6 July 2026

Verb

Timpson made her first start Friday, filling in for All-Star center Aliyah Boston, who missed her third game of the season due to a right lower leg injury. — James Boyd, New York Times, 18 July 2026

The most prominent position that UM’s athletic department has filled in the portal has been quarterback, with Cam Ward, Carson Beck and now Darian Mensah signed to big-money deals the past three years. — Barry Jackson, Miami Herald, 17 July 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