What does "prone" mean?

Prone: Prostrate; flat; esp., lying with the face down; -- opposed to supine. Which, as the wind, Blew where it listed, laying all things prone. Byron.

Additional senses

  1. 2.Headlong; running downward or headlong. "Down thither prone in flight." Milton.
  2. 3.Sloping, with reference to a line or surface; declivous; inclined; not level. Since the floods demand, For their descent, a prone and sinking land. Blackmore.
  3. 4.Inclined; propense; disposed; -- applied to the mind or affections, usually in an ill sense. Followed by to. "Prone to mischief." Shak. Poets are nearly all prone to melancholy. Landor.

Sources