1. In Greek mythology, a shape-shifting sea god who was the shepard of Poseidon's seal flocks
2. a blind, aquatic salamander with permanent gills, found in caves
3. an inspirational Edmontonian DJ who fused breaks and house music
In poker, the river is the fifth commmunity card to come up and the river rat is a person who called all wagers, with no apparent hand and a minute chance of winning, in order to catch some miracle card and 'river' any legitamate betting/raising hands.
I flopped a set, pounded it the whole way, and that river rat Mario called all the way just to hit a gut-shot.