Source : Webster's Revised Unabridged Dictionary (1913)

Loin \Loin\, n. [OE. loine, OF. logne, F. longe, from (assumed)
   LL. lumbea, L. lumbus join. Cf. {Lends}, {Lumbar},
   {Nombles}.]
   That part of a human being or quadruped, which extends on
   either side of the spinal column between the hip bone and the
   false ribs. In human beings the loins are also called the
   reins. See Illust. of {Beef}.

Source : WordNet®

loin
     n 1: a cut of meat taken from the side and back of an animal
          between the ribs and the rump
     2: either side of the backbone between the hipbone and the ribs
        in humans as well as quadrupeds [syn: {lumbus}]