The Collaborative International Dictionary of English v.0.48:

Proclive \Pro*clive"\, a. [L. proclivis sloping, inclined; pro
   forward + clivus hill: cf. F. proclive. See Declivity, and
   cf. Proclivous.]
   Having a tendency by nature; prone; proclivous. [R.] --Mrs.
   Browning.
   [1913 Webster]