The meaning of FIRST CROSS is an animal produced by interbreeding members of two pure breeds —contrasted with mongrel and purebred.
partly from Middle English murther, from Old English morthor; partly from Middle English murdre, from Anglo-French, of Germanic origin; akin to Old English morthor; akin to Old High German mord murder, Latin mort-, mors death, mori to die, mortuus dead, Greek brotos mortal First Known ...