What is "rheid"

n. (context zoology English) Any member of the Rheidae.

A rheid is a non-molten solid that deforms by viscous flow at least a thousand times faster than it would deform elastically under the same applied stress. The term, which was coined by S. Warren Carey in 1953, has the same Greek root as rheology, the science of viscoelasticity and nonlinear flow.