Longman Dictionary of Contemporary English
pop quiz
noun
EXAMPLES FROM CORPUS
▪ After an uproar, beef will still have to pass a pop quiz.
Wiktionary
pop quiz
n. (context US English) A quiz or test given without warning or prior announcement.
WordNet
pop quiz
n. a quiz given without prior warning
Wikipedia
Pop Quiz
Pop Quiz was a British television quiz programme that originally aired on BBC1 from 4 July 1981 to 28 December 1984 with a Top of the Pops special on 4 January 1994 hosted by Mike Read. It was then revived from 21 May to 9 July 1994 on the same channel but this time hosted by Chris Tarrant. It was revived again on Red TV from 14 June to 30 August 2008 with Mike Read returning as host and again from 15 to 29 December 2011 on Vintage TV.