sleeper

Short definition from Wiktionary

Noun

1. 1
   Someone who sleeps.
2. 2
   That which lies dormant, as a law.
3. 3
   A spy, saboteur, or terrorist who lives unobtrusively in a community until activated by a prearranged signal; may be part of a sleeper cell.
4. 4
   A small starter earring, worn to prevent a piercing from closing.
5. 5
   A railway sleeping car.
6. 6
   A sleeper hold.
7. 7
   Something that achieves unexpected success after an interval of time.
8. 8
   Any of family Odontobutidae of goby-like bottom-feeding freshwater fish.
9. 9
   A nurse shark (family Ginglymostomatidae).
10. 10
    A type of pajama for a person, especially a child, that covers the whole body, including the feet.
11. 11
    An automobile which has been internally modified to excess, while retaining a mostly stock appearance in order to fool opponents in a drag race, or to avoid the attention of the police.
12. 12
    A sedative.
13. 13
    A bet placed on the gambling table and then forgotten about by the gambler.
14. 14
    A pod or similar device containing a person in cryosleep.
15. 15
    A railroad tie.
16. 16
    A structural beam in a floor running perpendicular to both the joists beneath and floorboards above.
17. 17
    A heavy floor timber in a ship's bottom.
18. 18
    The lowest, or bottom, tier of casks.

Verb

1. 1
   To mark a calf by cutting its ear.

Proper noun

1. 1
   A surname.