1. To complete something very quickly and without much effort. In this usage, a noun or pronoun can be used between "whack" and "off." It used to take me quite a while to write articles for this website, but I've gotten to the point where I can whack them off in under an hour. I just need to whack off a couple emails before I head home.

2. To cut something off or away, especially quickly, indelicately, or without finesse. In this usage, a noun or pronoun can be used between "whack" and "off." I had been growing my hair out since I was in junior high school, and then one day I decided to whack it all off. The knight whacked off the peasant's arm for his insubordination. Will you go out back and whack those branches off the tree? They're obstructing our view of the sea.

3. vulgar slang To masturbate, especially a man.

4. vulgar slang To bring someone else to orgasm with one's hand or hands, especially a male. In this usage, a noun or pronoun can be used between "whack" and "off."

1. In a state of physical or emotional exhaustion, especially such that one cannot think or react properly. I was so whacked out after that 12-hour flight that I had trouble following along with what people were saying to me. We were all a little whacked out by the time we got home from the marathon, so we just showered and went to bed early.

2. Intoxicated from drugs or alcohol, especially to the point of incoherence or belligerence. Tom was so whacked out at the party that he couldn't speak properly by the end of the night. No thanks, I don't like how whacked out I get when I smoke weed.