To deflate is to let the air out of something. If you deflate the tires on your brother's bike, he won't be able to ride it until he gets them pumped up again.

You can deflate anything that's full of air or another gas: an air mattress, an inflatable sled, a helium balloon, or the tires on your car. When something, like a hot air balloon, empties of air, you can also say it deflates. Figuratively, a person can also deflate when they are suddenly drained of self-assurance or cheer: "Hearing him criticize me in front of the class made me deflate."

Definitions of deflate

v release contained air or gas from

deflate the air mattress”
Type of:
release, turn
let (something) fall or spill from a container

v collapse by releasing contained air or gas

deflate a balloon”
Type of:
fold or close up

v become deflated or flaccid, as by losing air

“The balloons deflated
blow up, inflate
fill with gas or air
Type of:
decrease, diminish, fall, lessen
decrease in size, extent, or range

v reduce or lessen the size or importance of

“The bad review of his work deflated his self-confidence”
Type of:
deprecate, depreciate, vilipend

v produce deflation in

“The new measures deflated the economy”
cause prices to rise by increasing the available currency or credit
Type of:
alter, change, modify
cause to change; make different; cause a transformation

v reduce or cut back the amount or availability of, creating a decline in value or prices

deflate the currency”
increase the amount or availability of, creating a rise in value
Type of:
bring down, cut, cut back, cut down, reduce, trim, trim back, trim down
cut down on; make a reduction in

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