Descent; declivity; as, the proneness of a hill.

Inclination of mind, heart, or temper; propension; disposition; as, proneness to self-gratification.

The quality or state of being prone, or of bending downward; as, the proneness of beasts is opposed to the erectness of man.

The state of lying with the face down; -- opposed to supineness.

being disposed to do something; "accident proneness"