one who, or that which, thrashes grain; a thrashing machine.-a large and voracious shark (alopias vulpes), remarkable for the great length of the upper lobe of its tail, with which it beats, or thrashes, its prey. it is found both upon the american and the european coasts. called also fox shark, sea ape, sea fox, slasher, swingle-tail, and thrasher shark.-a name given to the brown thrush and other allied species. see brown thrush.-same as thrasher.