To grind or chew. It sounds like masturbate so dumb fucks who are too lazy to figure out its real definition assume it means masturbate. It's a funny word and has power.
Mom: Son, you have anotherphone call. Do you want me too tell them your eating diner?
Son: Yeah just tell them I'm mastacating! They'll deffinatley stop calling
It can easily be mistaken for masturbate. A very good word to play around with, it is; so much that I played around with a newspaper teacher's mind by using it in a piece of writing.
You're amasticator, aren't you?
Yes, you are, you bad, bad man.
You like to masticate meat.
Just admit it, yeah, yeah.