To be predictable, or basic
Stacy: Did you hear that Naomi got back together with her ex for the 15th time?
Addison: Yeah, thats so knack of her. Wouldn't have expected anything else
Stacy: She's so knack
A wack knuckle head. Someone who is corny and stupid at the same time.
She acted as if she was at the protest but actually showed up just to take pictures, she’s a knack.