Longman Dictionary of Contemporary English
under-the-counter
adjective
EXAMPLES FROM CORPUS
▪ Cynics would suggest that an under-the-counter version of this system still applies - but they would be wrong.
▪ Nothing under-the-counter about the six Salomes.
Wiktionary
under-the-counter
a. illicit, obtained or sold furtively.
WordNet
under-the-counter
adj. done or sold illicitly and secretly;
Usage examples of "under-the-counter".
He hurried to the small refrigerator in the corner, which was designed for under-the-counter use in restaurants and could be opened with a foot pedal.