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

Multiple choice or fill-in-the-blank exam questions could be quickly and objectively scored. — Beth Kania-Gosche, The Conversation, 22 Sep. 2026

In her absence, season 1 cohosts Star Jones and Debbie Matenopoulos are set to return to the show as fill-in cohosts, alongside fellow ex-panelists Lisa Ling and cohost Sherri Shepherd. — Joey Nolfi, Entertainment Weekly, 17 Sep. 2026

Verb

Late in the third quarter of an already rough afternoon, Missouri running back Jamal Roberts, filling in for All-American Ahmad Hardy, disappeared on his 18th carry of the day. — Noah White, Miami Herald, 4 Oct. 2026

By filling in those gaps at the time of retrieval with the most likely possibility, your memory system can actually be quicker and be more flexible and work online in a timely manner. — Allison Parshall, Scientific American, 3 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