A colloquialism common to Canadian dialects, usually being added to the end of a sentence. The spoken tone of the word implies something to the effect of "do you agree?" Yet, the social connotation of the conversation's context usually implies that the speaker assumes that the listener already does agree. Therefore when a listener is presented with the post-sentence interrogative "eh," both responding in affirmation, and not responding at all, is appropriate.
In short, it's a term used to assert one's own opinion while cautiously acknowledging that the listener is of the same opinion.
Guy 1: I was on my ski-doo the other day and I saw a moose eating a bucket of poutine.
Guy 2: Fuck off, eh?
Guy 1: That girl has a big set of hooters, eh?
*Guy 2 is silent*
*Guy hands waitress a tip*
Waitress: Thanks alot, eh?
*Guy walks away*
Guy 1: There's some shit on your face, eh?
*Guy 2 beats the shit out of Guy 1*