1.Definition: (of persons) taken advantage of

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

Related Adjective(s):exploited, victimised, victimized

2.Definition: employed in accomplishing something

"The principle of surprise is the most used and misused of all the principles of war"

3.Definition: previously used or owned by another

"Bought a secondhand (or used) car"

Related Adjective(s):secondhand