kablah is a word with many meanings. it can mean "hate", "kill", or "destruct" - depending on how used.
generally it's a curse-word and it should not be used around klingons, as they will take it as an invitation for a "duel till death".
Mel Gibson also uses this term when scaring strangers away from his propertys or when trying to kill somebody - this happens to the fact that all the world knows, that Mel Gibson is half klingon, half insane, half manbearpig.
"You nasty motherfucker killed my kitten, i'm gonna destroy you! Kablah!"
"How dare you to look at my fiance this way? You will pay for that - Kablah!"
"Die, die, die, KABLAH!"