Call center jargon. Short for "shit canned." It can be used to mean getting fired, but it is usually implied that you were canned for a stupid reason, usually called a bullshit reason. Call centers are notorious for making up lame excuses for firing employees in order to improve their financial forcast.
1) Usually means to get fired.
2) Depending on context, can also be an adjective that means roughly predefined.
1) My faggot boss canned me for reading TribalWar too much at work.
2) Canned chat items in a video game. Usually performed by entering a short combination of letters or numbers. Many times accompanied by a short voice clip.