One who makes annoying slurrrrrrping noises when they drink from a can.
That guy in the cubicle next to me is a total can slurper, I can hear him drinking that soda over my headphones. I could even hear him suckin up beers at the company picnic over the DJ.
A generally positive exclamation, along the lines of "way to go" or the slightly older "excellent!." Originally from the Jonathan Coulton song Flickr and popularized by the podcast BadPhilosophy. Also can be used as an agreement.