a person or thing that fills in, as a substitute, replacement, or insertion: The company used a fill-in for workers on vacation.
a brief, informative summary; a rundown.

Nearby words

  1. filing clerk,
  2. filings,
  3. filiopietistic,
  4. filipino,
  5. filister,
  6. fill away,
  7. fill in,
  8. fill light,
  9. fill out,
  10. fill someone's shoes

Origin of fill-in

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



verb (used with object)

to make full; put as much as can be held into: to fill a jar with water.
to occupy to the full capacity: Water filled the basin. The crowd filled the hall.
to supply to an extreme degree or plentifully: to fill a house with furniture; to fill the heart with joy.
to satisfy fully the hunger of; satiate: The roast beef filled the diners.
to put into a receptacle: to fill sand into a pail.
to be plentiful throughout: Fish filled the rivers.
to extend throughout; pervade completely: The odor filled the room.
to furnish with an occupant: The landlord filled the vacancy yesterday.
to provide (an office or opening) with an incumbent: The company is eager to fill the controllership.
to occupy and perform the duties of (a vacancy, position, post, etc.).
to supply the requirements or contents of (an order), as for goods; execute.
to supply (a blank space) with written matter, decorative work, etc.
to meet satisfactorily, as requirements: This book fills a great need.
to make up, compound, or otherwise provide the contents of (a medical prescription).
to stop up or close (a cavity, hole, etc.): to fill a tooth.
Cookery. to insert a filling into: to fill cupcakes with custard.
  1. to distend (a sail) by pressure of the wind so as to impart headway to a vessel.
  2. to brace (a yard) so that the sail will catch the wind on its after side.
to adulterate: to fill soaps with water.
Civil Engineering, Building Trades. to build up the level of (an area) with earth, stones, etc.

verb (used without object)

to become full: The hall filled rapidly. Our eyes filled with tears.
to increase in atmospheric pressure: a filling cyclone.
to become distended, as sails with the wind.


a full supply; enough to satisfy want or desire: to eat one's fill.
an amount of something sufficient for filling; charge.
Civil Engineering, Building Trades. a quantity of earth, stones, etc., for building up the level of an area of ground: These houses were built on fill.Compare backfill.
the feed and water in the digestive tract of a livestock animal, especially that consumed before marketing.

Verb Phrases

fill away, Nautical.
  1. to fall off the wind and proceed on a board.
  2. to brace the yards, so that sails that have been aback will stand full.
fill in,
  1. to supply missing or desired information: Fill in the facts of your business experience.
  2. to complete by adding detail, as a design or drawing: to fill in a sketch with shadow.
  3. to substitute for: to fill in for a colleague who is ill.
  4. to fill with some material: to fill in a crack with putty.
  5. supply (someone) with information: Please fill me in on the morning news.
fill out,
  1. to complete (a document, list, etc.) by supplying missing or desired information.
  2. to become larger, fuller, or rounder, as the figure: The children have begun to fill out since I saw them last.
fill up,
  1. to fill completely: to fill up a glass; to fill up a fuel tank.
  2. to become completely filled: The riverbed filled up as a result of the steady rains.

Origin of fill

before 900; Middle English fillen, Old English fyllan; cognate with German füllen, Gothic fulljan to make full; see full1

Related formsfill·a·ble, adjectivehalf-filled, adjectiveun·filled, adjectivewell-filled, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for fill in

fill in

verb (adverb)

(tr) to complete (a form, drawing, etc)
(intr) to act as a substitutea girl is filling in while the typist is away
(tr) to put material into (a hole or cavity), esp so as to make it level with a surface
(tr) informal to inform with facts or news
(tr) British slang to attack and injure severely

noun fill-in

a substitute
US informal a briefing to complete one's understanding


verb (mainly tr often foll by up)

(also intr) to make or become fullto fill up a bottle; the bath fills in two minutes
to occupy the whole ofthe party filled two floors of the house
to plug (a gap, crevice, cavity, etc)
to meet (a requirement or need) satisfactorily
to cover (a page or blank space) with writing, drawing, etc
to hold and perform the duties of (an office or position)
to appoint or elect an occupant to (an office or position)
building trades to build up (ground) with fill
(also intr) to swell or cause to swell with wind, as in manoeuvring the sails of a sailing vessel
to increase the bulk of by adding an inferior substance
poker to complete (a full house, etc) by drawing the cards needed
mainly US and Canadian to put together the necessary materials for (a prescription or order)
fill the bill informal to serve or perform adequately


material such as gravel, stones, etc, used to bring an area of ground up to a required level
one's fill the quantity needed to satisfy oneto eat your fill

Word Origin for fill

Old English fyllan; related to Old Frisian fella, Old Norse fylla, Gothic fulljan, Old High German fullen; see full 1, fulfil

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

Word Origin and History for fill in
Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with fill in

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.


Also, fill in for. Take someone's place, substitute for. For example, The understudy had to fill in at the last minute, or I can't come but my wife will fill in for me. Also see fill someone's shoes.


In addition to the idioms beginning with fill

  • filled to the brim
  • fill in
  • fill out
  • fill someone's shoes
  • fill the bill

also see:

  • back and fill
  • get one's fill of

Also see underfull.

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