What does "monkey" mean?

Additional senses

1. 2.The weight or hammer of a pile driver, that is, a very heavy mass of iron, which, being raised on high, falls on the head of the pile, and drives it into the earth; the falling weight of a drop hammer used in forging.
2. 3.A small trading vessel of the sixteenth century. Monkey boat. (Naut.) (a) A small boat used in docks. (b) A half-decked boat used on the River Thames. -- Monkey block (Naut.), a small single block strapped with a swivel. R. H. Dana, Jr. -- Monkey flower (Bot.), a plant of the genus Mimulus; -- so called from the appearance of its gaping corolla. Gray. -- Monkey gaff (Naut.), a light gaff attached to the topmast for the better display of signals at sea. -- Monkey jacket, a short closely fitting jacket, worn by sailors. -- Monkey rail (Naut.), a second and lighter rail raised about six inches above the quarter rail of a ship. -- Monkey shine, monkey trick. [Slang, U.S.] -- Monkey trick, a mischievous prank. Saintsbury. -- Monkey wheel. See Gin block, under 5th Gin. -- Monkey wrench, a wrench or spanner having a movable jaw.
3. 4.To act or treat as a monkey does; to ape; to act in a grotesque or meddlesome manner. To monkey with, to handle in a meddlesome manner. [Colloq.]