1. The equivalent of clapping in ice hockey, in which a player literally taps his stick against the ice, boards or glass to create a clapping sound. As with clapping, this is generally a congratulatory gesture, or sometimes a sign of respect or encouragement (as with a player leaving the rink with an injury).
2. Outside of the actual playing of hockey, the term may be used as above, or to give a shout-out, recognition, etc. for pretty much any reason. In this case, when used in writing (as in message boards, blogs, etc.) the term is often abbreviated as s/t.
1. Only an asshole doesn't give a stick tap when they're finished playing the national anthem.
2. S/t to Casey for pointing out that shortcut. I had no idea it was there!