Definition of stick caterpillar in US English:

stick caterpillar

noun

  • 1A caterpillar of a geometrid moth (family Geometridae), which resembles a stick or twig and typically holds itself erect and motionless on its prolegs when disturbed.

  • 2†a stick insect (family Phasmida) (obsolete).

Origin

Mid 19th century; earliest use found in Gardeners' Chronicle.