A harmless colubrid snake, Storeria occipitomaculata, which is typically brown with a bright red belly, of eastern North America; (formerly also) Kirtland's water snake, Clonophis kirtlandii.
Origin
Early 19th century.
Definition of red-bellied snake in US English:
red-bellied snake
noun
A harmless colubrid snake, Storeria occipitomaculata, which is typically brown with a bright red belly, of eastern North America; (formerly also) Kirtland's water snake, Clonophis kirtlandii.