balloon

Concise Oxford English Dictionary © 2008 Oxford University Press:
balloon/bəˈluːn/

▶noun

• 1 a small rubber sac which is inflated and used as a child's toy or a decoration.

• 2 a large bag filled with hot air or gas to make it rise in the air, typically having a basket for passengers.

• 3 a rounded outline in which the words or thoughts of characters in a comic strip or cartoon are written.

• 4 a large rounded drinking glass, used especially for brandy.

• 5 Scottish informal a stupid person.

▶verb

• 1 swell out in a spherical shape.

  ■ increase rapidly.

• 2 travel by hot-air balloon.

• 3 Brit. (with reference to a ball) lob or be lobbed high in the air.

– phrases
when the balloon goes up informal when the action or trouble starts.

– derivatives
ballooner noun,
ballooning noun,
balloonist noun.

– origin C16 (orig. denoting a game played with a large inflated leather ball): from Fr. ballon or Ital. ballone ‘large ball’.