Concise Bible Dictionary:
In the East these are usually small, every family having its own mill. A woman, or sometimes two sit at the mill, turning the upper stone, casting in the grain occasionally through a hole in it, Larger mills are also referred to, the stone being turned by an ass (Num. 11:8; Matt. 18:6; Mark 9:42; Rev. 18:21-22).
Strong’s Dictionary of Greek Words:
Meaning:
apparently a primary word; a stone (literally or figuratively)
KJV Usage:
(mill-, stumbling-)stone