(noun)
a ring of fur or features on the neck of an animal or bird, often projecting and/or brightly-colored;
e.g. The males of the species are marked by a ruff of fur on the back of the neck.
(noun)
a common wading bird (a sandpiper) found in Eurasia, whose males have a large ring of colored feathers on their necks, used for display purposes during breeding season;
e.g. We were able to photograph the ruff and hear its birdcall.
(noun)
a small fish that is found in fresh water in Eurasia, belonging to the perch family;
e.g. I could only catch a ruff and a few other small fish.