thrash 
(thrăsh)
(thrăsh)v. thrashed, thrash·ing, thrash·es
v.tr.
1.
a. To strike or beat, especially repeatedly with a flail or stick. See Synonyms at beat.
b. To strike violently; batter: winds that thrashed the boat.
2. To swing or strike in a manner suggesting the action of a flail: The alligator thrashed its tail.
3. To defeat soundly or decisively.
4. To thresh (grain).
5. To sail (a boat) against opposing winds or tides.
v.intr.
1. To move wildly or violently: squirrels thrashing about in a cage.
2. To strike or flail.
3. To thresh.
4. To sail against opposing tides or winds.
n.
Phrasal Verbs: 1. The act or an instance of thrashing: "We sat on, listening to the thrash of night trees" (Roger Angell).
2. Music See speed metal.
thrash about (or around)
To struggle to decide or determine something: advisers thrashing about trying to develop a new policy.
thrash out
To discuss fully or produce by discussion: thrashed out their differences; thrashed out an agreement.
[Variant of THRESH.]
thrasher n.