[ fil-in ]
See synonyms for fill-in on
  1. a person or thing that fills in, as a substitute, replacement, or insertion: The company used a fill-in for workers on vacation.

  2. a brief, informative summary; a rundown.

Origin of fill-in

First recorded in 1915–20; noun use of verb phrase fill in

Words Nearby fill-in Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use fill-in in a sentence

British Dictionary definitions for fill in

fill in

  1. (tr) to complete (a form, drawing, etc)

  2. (intr) to act as a substitute: a girl is filling in while the typist is away

  1. (tr) to put material into (a hole or cavity), esp so as to make it level with a surface

  2. (tr) informal to inform with facts or news

  3. (tr) British slang to attack and injure severely

  1. a substitute

  2. US informal a briefing to complete one's understanding

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with fill-in


Complete something, especially by supplying more information or detail. For example, Be sure to fill in your salary history. It is also put as fill in the blanks, as in We'll rely on Mary to fill in the blanks. Yet another related usage is fill someone in, as in I couldn't attend, so will you fill me in? The first term dates from the mid-1800s; the others from the first half of the 1900s. Also see fill out.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.