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.
(tr) to complete (a form, drawing, etc)
(intr) to act as a substitute
a 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
informal (tr) to inform with facts or news
slang (tr) to attack and injure severely
a substitute
informal a briefing to complete one's understanding
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 .
First recorded in 1915–20; noun use of verb phrase fill in
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
When their All-Star forward Jalen Williams suffered a hamstring injury, they had an appropriate fill-in to call upon: a backup big man named, coincidentally, Jaylin Williams.
From The Wall Street Journal ● May 7, 2026
He will also serve as a lead correspondent for “48 Hours,” contribute to “60 Minutes,” and act as a fill-in anchor for CBS’s flagship broadcasts, she said.
From The Wall Street Journal ● Dec. 9, 2025
Since early last week, fill-in hosts have been substituting for O’Kelly.
From Los Angeles Times ● Oct. 15, 2025
Chicago’s replacement team was nicknamed the “Spare Bears” and Payton was the quarterback of that fill-in squad.
From Los Angeles Times ● Sep. 20, 2025
He was a kind of fill-in speaker, a holy handyman.
From "Go Tell It on the Mountain" by James Baldwin
McElwee finds images both startling and serene; videos that fill in gaps he couldn’t on his own.
From Salon ● Jul. 24, 2026
The findings help fill in the missing steps of a larger cycle.
From Science Daily ● Jul. 18, 2026
For example, you could work 30 hours a week at the bar, then fill in at the yoga studio and take on consulting work when you have the bandwidth or need the extra cash.
From MarketWatch ● Jul. 13, 2026
“We’ve got guys that can fill in and have to be ready for the opportunity to step up,” midfielder Tyler Adams said.
From Los Angeles Times ● Jul. 3, 2026
“You can fill in When,” Joe pointed out.
From "Mystery Map (The Hardy Boys: Secret Files, #3)" by Franklin W. Dixon
Maxwell noted that his work had been covered by knowledgeable fill-ins from out of state.
From Salon ● Jul. 24, 2025
In one sense, Stewart is the latest in a line of celebrity fill-ins who have hosted “The Daily Show” since Trevor Noah left in December 2022.
From New York Times ● Feb. 13, 2024
McAvoy was one of three regulars on the blue line that the Bruins didn’t have, making the performance of fill-ins like rookie Lohrei even more impressive.
From Washington Times ● Nov. 3, 2023
Several Jaguars could be considered potential fill-ins to help during bye weeks, mainly Lawrence, Etienne, Robinson, Christian Kirk and Engram.
From Seattle Times ● Oct. 20, 2022
The conga drum player was especially wild, playing insane fill-ins all over the place.
From "Drums, Girls, and Dangerous Pie" by Jordan Sonnenblick
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
