A buzzer rock is a player with a low points per game average who generally does not buzz in more than a few times per tournament. A typical buzzer rock will have a stat line of something like 2 tossups and 0 interrupts in 10 games for a 2.00 points per game average.
The Oxford University Quiz Society's Lexicon defines a buzzer rock as "A player whose sole purpose on a team is to make up the numbers, or be good-looking in the hope of getting on University Challenge. Also called 'warm body'." It is unknown whether this is an example of lexical convergent evolution or whether Muellerisms have indeed crossed the Atlantic.