brightly-coloured rubber bag that is filled with air, used as a child's toy or a decoration （用作玩具或装饰品的）气球. 
(also hot-`air balloon) large flexible bag filled with hot air or gas to make it rise in the air, often carrying a basket, etc for passengers 热气气球（常悬有吊篮等以载人）. 
(in strip cartoons, etc) shape like a balloon (ie round with a narrow neck) in which speech is shown （连环画等）供写对白的气球状线条圈（即带狭颈的圆圈）. 
(idm 习语) when the bal`loon goes up (infml 口) when expected trouble begins 当意料中的麻烦到来时: I don't want to be around when the balloon goes up. 要出事了, 我趁早离开是非之地.> balloon v [I]
1 swell out like a balloon 膨胀如气球: Her skirt ballooned in the wind. 她的裙子让风吹得鼓起 来了.
2 (usu 通常作 go ballooning) travel in a balloon as a sport 乘气球（作为运动）: They like to go ballooning at weekends. 他们周末喜欢乘气球玩.
balloonist n person who travels by balloon, esp as a sport 乘气球的人（尤指作为运动）.