An action figure is a magically animated figure of people or animals.
At the 1994 Quidditch World Cup, Ron bought a small model of Viktor Krum, the famous Bulgarian Seeker, which walked around and scowled (GF7) and even mimicked the real Viktor Krum’s posture and way of walking (GF9). After Viktor Krum took Hermione to the Yule Ball, Harry found the arm of the little model lying on the floor of the boys’ dormitory. Ron had apparently broken it (GF24).
Harry and the other Triwizard champions drew small model dragons out of a silk bag. The type of model indicated which dragon they had to face. Harry drew the Hungarian Horntail. Each tiny model moved its wings and snarled; Harry’s even curled up and went to sleep the night after the first task (GF20).
Xenophilius Lovegood and his daughter Luna have delicately made models of creatures, all flapping wings or snapping jaws, hanging from their ceiling at home. Harry couldn’t recognize them after four years of Care of Magical Creatures lessons, so they must have been pretty odd (DH20).
An action figure from the Wizarding world is much more likely to actually be active than one made for Muggles, much like Wizarding photographs.
Muggle definition of Action figures: Wikipedia
From the Web
Harry Potter Wiki: Action figure