Something that sits between two men at a restaurant, movie, or in a car. Can be a female or a tub of popcorn. The buffer prevents anyone from thinking the two males are "homos" and might be dating. Sometimes the fag buffer is actually a front so that two fags can go out and still be perceived as straight. The fag buffer usually gets a good meal, a movie and collects a lot of material for later extortion.
I went out with Bob and Gene last night and had to play fag buffer all evening. Straight men are so childish!