Don’t be intimidated by the bulk of the dictionary on your desk. If you look in it, you’ll see that bulk is a small word used to talk about large things.
Bulk has a variety of meanings that all involve something large, like the bulk of a ship in the harbor, or the excess bulk of your overweight cat. Bulk can also mean “majority,” as when the bulk of your diet is tater tots and guacamole. You can expect to put on a lot of bulk if you eat like that.