When you either accidentally or deliberately to be
ironic type "smile" with your right
hand on the wrong
keys.
Originated in text-based MUDs in the 90s where users would type commands into the console to "emote."
Example
1.
Person
1: I love you so much, dearest.
Person 2:
Sweet! *SNUKE*
Example 2.
"say I just slayed that level 50 dragon!"
You say: I just slayed that level 50 dragon!
"Hrothgar: snuke"
Hrothgar tries to type "smile" but his hands are on the wrong keys!