1 a person or animal that sleeps.
2 Brit. a wooden or concrete beam laid horizontally as a support, esp. for railway track.
3 a a sleeping-car. b a berth in this.
4 Brit. a ring worn in a pierced ear to keep the hole from closing.
5 a thing that is suddenly successful after being undistinguished.
6 a sleeping-suit.
7 a spy or saboteur etc. who remains inactive while establishing a secure position.
Useful english dictionary. 2012.