noun descent; declivity; as, the proneness of a hill.
2. proneness ·noun the state of lying with the face down;
opposed to supineness.
3. proneness ·noun inclination of mind, heart, or temper; propension; disposition; as, proneness to self-gratification.
4. proneness ·noun the quality or state of being prone, or of bending downward; as, the proneness of beasts is opposed to the erectness of man.