Rootkit: a way of hiding malicious programs (malware).
Heuristic: any way of discovering malware that is not based on finding exactly the same code signature.
Avast: Old sea dog's word for " stop", as in, "Avast there ye scurvy dogs, sea lice, vermin, pirates, sea gherkins, baboons, buccaneers, filibusters, gallows-fodder!".
