From WordNet (r) 3.0 (2006) [wn]:
bombshell
n 1: an entertainer who has a sensational effect; "she was a
blonde bombshell"
2: a shocking surprise; "news of the attack came like a
bombshell" [syn: bombshell, thunderbolt, thunderclap]
3: an explosive bomb or artillery shell
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Bombshell \Bomb"shell`\, n.
1. A bomb. See Bomb, n.
[1913 Webster]
2. something or someone that stuns or amazes, especially
suddenly and unexpectedly; as, the news of the president's
affair was a political bombshell; a blonde bombshell.
[PJC]