The adverb of 'spry': doing something in a quick, light, energetic way, when you would not quite expect it of the person's age. It attaches to verbs of movement — someone steps spryly off a bus, walks spryly up a hill, moves spryly across the room. Like 'spry', the word carries a small note of pleasant surprise, so the person is nearly always old. It is a fairly rare word; most people say 'he moved quickly for his age' instead. You will meet it in writing more than in speech.