Adjectives

(s)secondhandderived from what is primary or original; not firsthand“a secondhand report”, “a secondhand account of a memory of something once read”, “most of our knowledge is secondhand”
(s)secondhand, usedpreviously used or owned by another“bought a secondhand (or used) car”

Adverbs

(r)secondhandby indirect means“I heard about it only secondhand or thirdhand”, “he prefers to buy secondhand”