Definition
to be very close to reaching a particular age, usually an older one
將近60、70等歲（通常指高齡）
He still looks young, but he's actually knocking on 60.
他看起來還很年輕，但實際上已經快60歲了。
My mother is knocking on 70, but she's still very active.
我母親快70歲了，但她仍然非常活躍。
Although he's knocking on 80, he still goes for a walk every day.
雖然他快80歲了，但他仍然每天去散步。