A-nôr'/tho-scōpe, n.

n. [Gr. ἀν priv., ὀρθός, straight, and σκοπεῖν, to see.] An instrument for producing a peculiar kind of optical illusion by means of two disks rotating rapidly opposite to each other. The posterior one is transparent, and has certain distorted figures painted upon it: the first is opaque, but pierced with a number of narrow slits through which the figures on the posterior disk are viewed.