Source : Webster's Revised Unabridged Dictionary (1913)

Lye \Lye\, n.
   A falsehood. [Obs.] See {Lie}.

Lye \Lye\, n. [Written also {lie} and {ley}.] [AS. le['a]h; akin
   to D. loog, OHG. louga, G. lauge; cf. Icel. laug a bath, a
   hot spring.]
   A strong caustic alkaline solution of potassium salts,
   obtained by leaching wood ashes. It is much used in making
   soap, etc.

Lye \Lye\, n. (Railroad)
   A short side line, connected with the main line; a turn-out;
   a siding. [Eng.]

Source : WordNet®

lye
     n : a strong solution of sodium or potassium hydroxide