Source : Webster's Revised Unabridged Dictionary (1913)

Precipitous \Pre*cip"i*tous\, a. [L. praeceps, -cipitis: cf. OF.
   precipiteux. See {Precipice}.]
   1. Steep, like a precipice; as, a precipitous cliff or
      mountain.

   2. Headlong; as, precipitous fall.

   3. Hasty; rash; quick; sudden; precipitate; as, precipitous
      attempts. --Sir T. Browne. ``Marian's low, precipitous
      `Hush!''' --Mrs. Browning. -- {Pre*cip"i*tous*ly}, adv. --
      {Pre*cip"i*tous*ness}, n.

Source : WordNet®

precipitousness
     n : the property possessed by a slope that is very steep [syn: {abruptness},
          {steepness}] [ant: {gradualness}]