WordNet sense 1 (the soft brown fur of the beaver):

beaver fur

WordNet sense 2 (a native or resident of Oregon):

Oregonian

WordNet sense 3 (a man's hat with a tall crown; usually covered with silk or with beaver fur):

stovepipe, topper, dress hat, high hat, opera hat, silk hat, top hat

WordNet sense 4 (a hat made with the fur of a beaver (or similar material)):

castor

WordNet sense 5 (work hard on something):

beaver away