Source : Webster's Revised Unabridged Dictionary (1913)

Irreligious \Ir`re*li"gious\, a. [L. irreligiosus: cf. F.
   irr['e]ligieux.]
   1. Destitute of religion; not controlled by religious motives
      or principles; ungodly. Cf. {Impious}.

            Shame and reproach are generally the portion of the
            impious and irreligious.              --South.

   2. Indicating a want of religion; profane; wicked; as,
      irreligious speech.

Source : WordNet®

irreligious
     adj : hostile or indifferent to religion [ant: {religious}]