flail

Short definition from Wiktionary

Noun

1. 1
   A tool used for threshing, consisting of a long handle (handstock) with a shorter stick (swipple or swingle) attached with a short piece of chain, thong or similar material.
2. 2
   A weapon which has the (usually spherical) striking part attached to the handle with a flexible joint such as a chain.
3. 3
   Part of a rotating device, often used for cutting vegetation.

Verb

1. 1
   To beat using a flail or similar implement.
2. 2
   To wave or swing vigorously
3. 3
   To thresh.
4. 4
   To move like a flail.