Definition of Oversleep

Babylon English Dictionary
sleep too much, sleep too late
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Oversleep Definition from Language, Idioms & Slang Dictionaries & Glossaries
Webster's Revised Unabridged Dictionary (1913)
(v. t.)
To sleep beyond; as, to oversleep one's self or one's usual hour of rising.
  
(v. i.)
To sleep too long.
  
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. About
WordNet 2.0

Verb
1. sleep longer than intended
(entail) sleep, kip, slumber, log Z's, catch some Z's