Definition of "illicit"

Such migrants may violate our laws against illicit entry, but if that's all they do then they are trespassers, not criminals.

2008 January 8, Madeleine Albright, Memo to the President Elect: How We Can Restore America's Reputation and Leadership, New York: HarperCollins, page 225

I only can properly enjoy carol services if I am having an illicit affair with someone in the congregation.

1993, Alan Clark, Diaries: In Power 1983-1992, London: Weidenfeld & Nicolson

Ayşe Erkoç learned long ago that the secret of doing anything illicit in Istanbul is to do it in full public gaze in the clear light of day. No one ever questions the legitimacy of the blatant.

2010 July 29, Ian McDonald, The Dervish House‎

A large number of studies, however, have reported that it is rare for the user of 'hard' drugs not to have initiated cannabis use prior to the other illicits.

2011, Shane Darke, The Life of the Heroin User: Typical Beginnings, Trajectories and Outcomes