The Collaborative International Dictionary of English v.0.48:

Falling \Fall"ing\, a. & n.
   from Fall, v. i.
   [1913 Webster]

   Falling away, Falling off, etc. See To fall away, To
      fall off, etc., under Fall, v. i.

   Falling band, the plain, broad, linen collar turning down
      over the doublet, worn in the early part of the 17th
      century.

   Falling sickness (Med.), epilepsy. --Shak.

   Falling star. (Astron.) See Shooting star.

   Falling stone, a stone falling through the atmosphere; a
      meteorite; an a["e]rolite.

   Falling tide, the ebb tide.

   Falling weather, a rainy season. [Colloq.] --Bartlett.
      [1913 Webster]

WordNet (r) 3.0 (2006):

falling off
    n 1: a noticeable deterioration in performance or quality; "the
         team went into a slump"; "a gradual slack in output"; "a
         drop-off in attendance"; "a falloff in quality" [syn:
         slump, slack, drop-off, falloff, falling off]