'Illegal' definitions:

Definition of 'illegal'

(from WordNet)
adjective
Prohibited by law or by official or accepted rules; "an illegal chess move" [ant: legal]

Definition of 'Illegal'

From: GCIDE
  • Illegal \Il*le"gal\, a. [Pref. il- not + legal: cf. F. ill['e]gal.] Not according to, or authorized by, law; specif., contrary to, or in violation of, human law; unlawful; illicit; hence, immoral; as, an illegal act; illegal trade; illegal love. --Bp. Burnet. [1913 Webster]