Definition of rain frog:
(n) :
Any of many species of frogs in diverse genera:
(n) :
(US) A tree frog, especially, a spring peeper.
(n) :
Those of family Brevicepitidae, of Africa
(n) :
Those of family Eleutherodactylidae, of the Americas
(n) :
Austrochaperina pluvialis (family Microhylidae), of Australia
(n) :
Craugastor (Craugastoridae), of the Neotropics