A balloon filled with gas that is lighter than air; especially (now frequently historical) one supporting beneath it a basket for passengers. Often contrasted with hot-air balloon.
Origin
Late 18th century; earliest use found in The Morning Post. From gas + balloon.
Definition of gas balloon in US English:
gas balloon
nounˈɡas bəˌluːn
A balloon filled with gas that is lighter than air; especially (now frequently historical) one supporting beneath it a basket for passengers. Often contrasted with hot-air balloon.
Origin
Late 18th century; earliest use found in The Morning Post. From gas + balloon.