n.a thin explosive device inside an envelope or package and detonated when opened
同义词：letter bombparcel bombpackage bomb
v.send an explosive to
同义词：letter bomb
英汉双解大词典
letter bomb(letterbombs)
1.
N-COUNT（可数名词）
A letter bomb is a small bomb which is disguised as a letter or package and sent to someone through the mail. It is designed to explode when it is opened. 书信(或邮包)炸弹