The Collaborative International Dictionary of English v.0.48:

Poteen \Po*teen"\, Potheen \Po*theen"\, n. [Ir. poitin a small
   pot, whisky made in private stills; cf. pota pot, fr. E.
   pot.]
   Whisky; especially whisky distilled in a small way privately
   or illicitly by the Irish peasantry. [Written also
   potteen.]
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Poteen \Po*teen"\, n. [, poitin a small pot.]
   especially, whisky illicitly distilled by the Irish
   peasantry.
   [1913 Webster]

WordNet (r) 3.0 (2006):

poteen
    n 1: unlawfully distilled Irish whiskey