A silly person who is often really happy all the time for no apparent reason. They are also weird and do weird stuff.
TheBaz: She is such a loaf, everything she does is pretty loafy
Dasmien: Did you hear she soiled herself on stage?
TheBaz: Yeah that's pretty loafy. There's some pictures of her looking loafy, too
Women who tend to be on the hefty side who intimidate those around them. Usually when they are a tad intoxicated and trying to make sexual advances. Can also be used in the context of scary, large women seen in everyday life.
Dude, do you see that girl over there? What a loaf!