Bombast is a noun meaning pretentious or boastful talk. If your football coach is known for his bombast, he probably gives a pompous speech before each game about the greatness of the team and, of course, his coaching.
Originally, bombast was cotton padding used to stuff or pad things like seat cushions. The meaning was extended to include padded and overstuffed speaking or writing, especially speech that's pretentious and showy. Other words with bombast at their roots include the adjective bombastic and the adverb bombastically. For all your coach's bluster and bombast, he's a pretty nice guy — too bad his overblown rhetoric turns people off before they get to know him.