'Liar' definitions:

Definition of 'liar'

From: WordNet
noun
A person who has lied or who lies repeatedly [syn: liar, prevaricator] [ant: square shooter, straight arrow, straight shooter]

Definition of 'Liar'

From: GCIDE
  • Liar \Li"ar\ (l[imac]"[~e]r), n. [OE. liere. See Lie to falsify.] A person who knowingly utters falsehood; one who lies. [1913 Webster]

Synonyms of 'liar'

From: Moby Thesaurus