'Insomnia' definitions:

Definition of 'insomnia'

From: WordNet
noun
An inability to sleep; chronic sleeplessness [ant: hypersomnia]

Definition of 'Insomnia'

From: GCIDE
  • Insomnia \In*som"ni*a\, n. [L., fr. insomnis sleepless; pref. in- not + somnus sleep.] Lack of sleep; inability to sleep, especially when chronic; wakefulness; sleeplessness. [1913 Webster]