Thau'ma-trōpe, n.

n. [Gr. θαῦμα, a wonder, and τρέπειν, to turn.] (Opt.) An optical toy or instrument for showing the persistence of an impression upon the eye after the luminous object is withdrawn. It consists of a card having on its opposite faces figures of two different objects, or halves of the same object, as a bird and a cage, which, on whirling the card rapidly round a diameter by the strings that hold it, appear to the eye combined in a single picture, as the bird in its cage, &c.