Monkeying around' is an expression used to describe playful or mischievous behavior. It comes from the word 'MONKEY, ' which refers to a small primate with a reputation for being curious and mischievous. The crossword solution APERY is a word that means 'imitating or mimicking MONKEY behavior.' Therefore, the term 'monkeying around' can be summarized as playful or mischievous behavior that mimics the behavior of monkeys.