large tough nonrigid bag filled with gas or heated air
"The hot-air balloon gently drifted over the valley as it rose into the clear sky."
small thin inflatable rubber bag with narrow neck
"The child carefully blew into the narrow neck of the balloon until it expanded into a round shape."
An inflatable buoyant object, often (but not necessarily) round and flexible.
"The child let go of their red balloon, watching it float gently upward into the sky."
In plain English: A balloon is an inflatable bag made of rubber or plastic that floats when filled with air or helium.
"We filled the red balloon with helium and released it into the sky."
Usage: As a noun, the word refers to an inflated rubber toy used in parties or celebrations that is typically filled with air or helium. When used as a verb, it describes something expanding quickly, such as prices rising sharply or cheeks flushing red from embarrassment.
ride in a hot-air balloon
"He tried to balloon around the earth but storms forced him to land in China"
To increase or expand rapidly.
"The crowd began to balloon as more fans arrived at the stadium."
In plain English: To balloon means to grow very large and round quickly, often because of pressure from inside.
"Her face turned red and seemed to balloon with anger when she heard the news."
The word balloon first appeared in English around 1591 to describe an inflated leather ball used for games, borrowing directly from Italian pallone meaning "large ball." This term likely traveled through Middle French before entering English usage.