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

Dell filled in at the end of the loss to the Giants after Noel got hurt and was out there for the fair catch after the Chargers' second drive of the day stalled. — Peter Warren, Houston Chronicle, 8 Nov. 2026

Tommy Carr, whose grandfathers are College Hall of Famers and brother is Notre Dame's quarterback, successfully filled in for Underwood in a comeback win against the Nittany Lions. — ABC News, 8 Nov. 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