A blooper is a mistake, especially an embarrassing one that's witnessed by other people. Your professor may be famous for his colorful bow ties and his frequent bloopers.
You can use the word blooper to describe any gaffe or faux pas that makes you blush. Often films and TV shows will keep a reel of bloopers that were caught on camera — generally mistakes or flubbed lines by actors. The word was first used in the 1940s in the theater world, from US baseball slang, meaning "a high fly ball that an outfielder doesn't catch."