Real Dictionary

wolf whistle in American English
a characteristic whistle of two notes, the second sliding from a high to a low note, made by a man to express his admiration of a sexually attractive woman
noun: a wolf call made by whistling, often characterized by two sliding sounds, a peal up to a higher note and then one up to a lower note and down

wolf whistle in British English
noun: a whistle made to express admiration of someone's appearance
verb: to make such a whistle (at someone)

wolf-whistle
verb: If someone wolf-whistles, they make a whistling sound with a short rising note and a longer falling note. Some people wolf-whistle to show that they find someone attractive.

wolf-whistle in British English
to whistle at someone to express admiration of their appearance