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1.
1. Verb. To Shneer: To "have the craic" or mess, but with intent which could be considered anywhere from mischievous to malicious.

2. Noun. eg "To have the shneer" The act of shneering is known as "the shneer"
Person 1: What did you do last night?
Person 2: Oh, we went out on the shneer.
Person 1: Yeah? What did you do?
Person 2: We egged some drunk people, drew a uterus on a lamppost and yelled abuse at ZamZams.
by CianBreathnach November 06, 2011
 
2.
Craic, but better. The best of times. The essence of hanging out with the best of friends, doing the best of things.

Originated in Dundalk, Ireland.
Gooch sock last night was great shneer.
We had the best ride, our car was the shneer car.
As an exclamation: shneer!
by Kashmir90 August 10, 2010