a portable loudspeaker with built-in microphone and amplifier
同义词：loud-hailer
bullhorn详细解释
bull.horn n.（名词）A portable device consisting of a microphone attached to a loudspeaker, used especially to amplify the voice.手提式扩音器：一种便携的由麦克风和扩音器连在一起的设备，专用来扩大声音
