The Collaborative International Dictionary of English v.0.48:

Janus \Ja"nus\, n. [L. See January.] (Rom. Antiq.)
   A Latin deity represented with two faces looking in opposite
   directions. Numa is said to have dedicated to Janus the
   covered passage at Rome, near the Forum, which is usually
   called the Temple of Janus. This passage was open in war and
   closed in peace. --Dr. W. Smith.
   [1913 Webster]

   Janus cloth, a fabric having both sides dressed, the sides
      being of different colors, -- used for reversible
      garments.
      [1913 Webster]