1. prone, prostrate - lying face downward
   Antonyms: erect, vertical, upright (indirect, via unerect)
   
2. prone - having a tendency (to); often used in combination; "a child prone to mischief"; "failure-prone"
   Antonym: disinclined (indirect, via inclined)
   

Prone

Part of Speech: Adjective

Sense 1:

Definition: lying flat or face down

Example: He was prone on the ground, unable to move.

Sense 2:

Definition: having a tendency or inclination towards something

Example: She is prone to overthinking situations.

Sense 3:

Definition: subject or susceptible to something

Example: He is prone to sunburn because of his fair skin.