This is a reference to the song "Post To Be" by Omarion. In the song, Jhene Aiko refers to her booty as groceries. It is a sex term. He eats food and he figuratively eats her ass in a sexual way. It is now a pop culture reference. Instead of ass, one says groceries. Only in a sexual context.
1.)-prep. phrase- a polite, and usually deceptive, manner a man has to say that he is busy masturbating to orgasm.
Usually used in the presence of young children and/or parents/grand parents where one doesn't want to use the more obscene terminology, or otherwise wants to fly below the radar.