episcotister

or e·pis·ko·tist·er

[uh-pis-kuh-tis-ter, ep-i-skuh-tis-ter]

noun

a disk with a sector removed that when rotated in front of a light source allows the periodic passage of flashes of light: used in studying the motion of a body.

Origin of episcotister

1900–05; < Greek episkot(ízein) to overshadow (see epi-, scotia, -ize) + -ist + -er¹