1. To hit or attempt to hit someone or something with one's fist or some kind of instrument. I took a whack at him for making such a lewd suggestion. Try taking a whack at it—that usually gets the motor running again.

2. To attempt (to do) something; to take a turn trying (to do) something. Well, I haven't fixed a motor in nearly 10 years, but I'll certainly take a whack at it. You had your chance trying to break the piñata, now let your sister take a whack at it.