Definitions of thrasher:

• noun:   thrush-like American songbird able to mimic other birdsongs
• noun:   large pelagic shark of warm seas with a whiplike tail used to round up small fish on which to feed
• noun:   a farm machine for separating seeds or grain from the husks and straw
• name:  A surname (common: 1 in 20000 families; popularity rank in the U.S.: #2529)