Craic is the Irish word that most confuses outsiders, yet it is a relatively simple concept. It is the atmosphere, fun, carry on surrounding a particular night out. "How was the craic?" is the first question uppermost in most young Irish minds after a weekend.

Good craic: A fairly ok night out, fun but nothing too amazing.
Mighty craic: Better than good craic, not quite at the highest level, someone did some crazy stuff maybe.
Savage craic: Almost there, great night all together, everyone on top firm, Guinness flowing, great jokes.
Deadly craic: A step above savage but not quit the Everest moment.
The craic was ninety: The nirvana of craic, everything was amazing, incredible, everyone hooked up, the pints were great. No one quite sure how the word ninety came into it--a famous Christy Moore song "The craic was ninety in the Isle of Man" maybe:
And lastly!
Minus craic: That's when a night goes wrong and essentially you'd have had more fun in a mausoleum.