The Collaborative International Dictionary of English v.0.48:

Beefsteak \Beef"steak`\ (b[=e]f"st[=a]k), n.
   A steak of beef; a slice of beef broiled or suitable for
   broiling.
   [1913 Webster]

WordNet (r) 3.0 (2006):

beefsteak
    n 1: a beef steak usually cooked by broiling