To hit random keys on your keyboard at a high speed when chatting online for an instant reaction to an otherwise problematic or over-joyous statement/event.
Qwerty spasms can also be used as conversation starters, online 'ice-breakers', or means of beginning a blog/online journal.
"what is it?"
"lolsrry, i thought a Qwerty Spasm would break the silence"
"...why another spasm?"
"bcuz, dude, i just lost the game"