(1):

(n.) One who, or that which, grinds.

(2):

(n.) One of the double teeth, used to grind or masticate the food; a molar.

(3):

(n.) The restless flycatcher (Seisura inquieta) of Australia; - called also restless thrush and volatile thrush. It makes a noise like a scissors grinder, to which the name alludes.