adj. The act of still having your virginity in college while being surrounded by drunken pussy 24/7. Drinking excessively almost everyday for no apparent reason while also going on explicitly long rants about nothing that have no relevance to the pertaining situation. Not showering for days at a time is also a trait of O'Callaghan. In summary, the act of completely embarrassing the Irish race one drunken night at a time.
a really nice person, who has a great personality. Very handsome and charming, can sometimes be misjudged by his lack of knowledge around the complications of thunder and bringing the bins in, but overall if you ever meet a Liam O'Callaghan, you are the luckiest person in the world