thresher shark noun1 •Any of the species of sharks in the genus Alopias, three of which are extant.When I was 12 years old, my father got me a boat and I went fishing off of Cape Cod. I hooked a scup and as I was reeling it in, I hooked a 4.5 foot baby thresher shark who proceeded to eat my boat. — 1975 formsthresher sharks
