• (a.) Tending to prevent sleep. • (n.) An antihypnotic agent.
An`ti·hyp·not'ic adjective (Medicine) Tending to prevent sleep. -- noun An antihypnotic agent. 
Type: Term Pronunciation: an′tē-hip-not′ik Definitions: 1. Preventing or tending to prevent sleep. 2. An arousing agent, or one antagonistic to sleep.
antihypnotic, anhypnotic Tending to prevent sleep; such as, a medicine, etc. that is used for this purpose.