fatter; fattest
1
: having a lot of extra flesh on your body : having a lot of body fat
The dog is getting fat because you feed him too much.
a cute, fat baby
I can't believe I've let myself get so fat.
a movie that has a lot of fat jokes [=jokes about fat people]
Note: Fat can be an insulting word when it is used to describe a person.
2
: having a full, rounded form
a fat belly
a fat, juicy peach
Note: A fat lip is a lip that is swollen because of injury, especially from being punched.
3
: unusually wide or thick
a fat book of poems
a fat envelope
a truck with fat tires
4
informal
: containing, providing, or costing a large amount of money
a fat bank account
He signed a fat contract.
The company offered her a fat salary.
a fat check [=a check for a large amount of money]
He had to pay a fat [=big] fine.
5
informal + disapproving
: successful or wealthy
The company grew fat on profits during the war.
6
baseball
: easy to hit
a fat pitch right down the middle of the plate
plural fats
1
: the soft flesh on the bodies of people and animals that helps keep the body warm and is used to store energy
people with excess body fat
a diet and exercise program to help you gain muscle and lose fat
exercises that burn fat = fat-burning exercises [=exercises that make your body use the fat it has stored]
2
: an oily solid or liquid substance in food
Nuts contain a lot of fat.
milk/bacon fat
Trim the fat from the meat before you cook it.
foods that are high in fat = foods with a high fat content
reducing dietary fat
a diet low in fat [=a low-fat diet]
a diet low in fats
saturated fats
fats like butter and olive oil
3
: an amount that is more than what is usual or needed : excess
trim the fat off/from the budget
Cite this Entry
“Fat.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/fat. Accessed 19 Jun. 2026.
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