/bu:m ||; bum/noun[C] 1 a period in which sth increases or develops very quickly 激增;繁荣;兴旺: There was a boom in car sales in the 1980s. 20世纪80年代,汽车销量激增。
2 [usu.sing] a loud deep sound 低沉的声音;隆隆声;嗡嗡声: the boom of distant guns 远处炮火的隆隆声
3 a long pole to which the sail of a boat is fixed. You move the boom to change the position of the sail. 张帆杆 ☞picture at boat 见 boat 插图