a large farm building for storing grain or keeping animals in 谷仓；畜棚；仓房 
a hay barn 干草棚 They live in a converted barn (= a barn that has been turned into a house). 他们住在由谷仓改成的房子里。
a large plain ugly building 简陋的大建筑物 - (North American English)
a building in which buses, trucks, etc. are kept when not being used （公共汽车、卡车等的）车库
Word OriginOld English bern, berern, from bere ‘barley’ + ern, ærn ‘house’.
Idioms
close, lock, etc. the barn door after the horse has escaped (North American English)
(British English close, lock, etc. the stable door after the horse has bolted)
to try to prevent or avoid loss or damage when it is already too late to do so 马跑了才去关厩门；贼走关门，为时已晚