Definitions of used:

• adjective:   employed in accomplishing something

  Example: "The principle of surprise is the most used and misused of all the principles of war- H.H.Arnold & I.C.Eaker"

• adjective:   previously used or owned by another

  Example: "Bought a secondhand (or used) car"

• adjective:   of persons; taken advantage of

  Example: "After going out of his way to help his friend get the job he felt not appreciated but used"