Being roughly between 45 and 65 years old; neither young nor elderly.
“A middle-aged woman is standing near the entrance, checking her phone.”
“There's a middle-aged couple sitting together on a park bench.”
Use this word to describe people's approximate age in Task 3, since examiners expect you to comment on age, appearance, and actions. Avoid guessing an exact number — 'middle-aged' is a safe, natural category to use.
Synonyms: in their forties or fifties, not particularly young, mature-looking