This is a Latin term meaning "what pleases" (said "kwode-lih-bet"), but the musical meaning can only be described as "a piece made up of a bunch of familiar stuff". Bits and pieces of popular melodies can be knitted together in a musical composition to make up a quodlibet. I've never actually seen this word notated on a piece before, but it's a word I always wished I had to describe pieces like Instant Concert, the piece in the video below. And here, like an early (winter holiday of choice) gift, the word appears, ready for use!
Note: I chose this version of this piece because of the unforeseen wackiness factor of the Australian police!