noun

• (historical) A whistle blown by a theatre-goer to express disapproval.
  "At what period was the custom of blowing catcalls at the theatre discontinued?"

verb

• (transitive) To make such an exclamation.
  "When Susan Seligson thinks about breasts — and, since she’s a DDD-endowed (touché) middle-aged woman who’s been groped and catcalled her whole life, that’s often, too — she thinks about ... her own DDDs."

noun

• (programming) In the Eiffel programming language, a run-time error caused by use of the wrong data type.
  "Java does not let you make members more private than they are in parent classes, so has no catcall problem for changing availability. Thus to avoid catcalls with export problems, you should adopt a once-public, always-public policy."