(1):

(n.) A channel or hollow worn in the earth by a current of water; a short deep portion of a torrent's bed when dry.

(2):

(n.) A large knife.

(3):

(n.) A grooved iron rail or tram plate.

(4):

(v. t.) To wear into a gully or into gullies.

(5):

(v. i.) To flow noisily.