A term originating in the game Starcarft, where two or more friends would create a public team game and all join the same team, with the expectation that they would be playing against un-coordinated strangers.
"Hey, I found another friend we can pubstomp with, I'll make a game called '3v3 for fun', join up"
verb. When an organized team of friends/clan members plays against a team of "pubs" - random people who join a public server.
The game is typically very one sided, despite the games being created under the false impression that it is going to be 'fair'.
Can apply to any team-oriented game, but the term is likely to have originated in DotA.
Can also be used as a noun, whereby the events described above occurs.
"Lets go pubstomp some noobs. I'll host"
"5v5 noobs only. nothing suss"
Used in Warcraft DotA
When organized groups of confidently good players go to a cybercafe/ventrilo and team up against random pub players with no prior association.
A team of friends decide to pubstomp, but it turns into an epic battle of skill and wit to see who can overcome who.