Longman Dictionary of Contemporary English
spot check
noun
EXAMPLES FROM OTHER ENTRIES
▪ Customs officers make random spot checks.
EXAMPLES FROM CORPUS
▪ Most drivers pass the spot check, not so this Volkswagen.
Wiktionary
spot check
alt. (context idiomatic English) A cursory inspection or examination or the inspection or examination of a sample of something. n. (context idiomatic English) A cursory inspection or examination or the inspection or examination of a sample of something. vb. (context idiomatic English) To inspect or examine briefly, or by sampling.
WordNet
spot check
n. a check on work performance or product quality made at random times without warning; "spot checks ensure a high level of performance by employees"