working or acting merely for money or other reward; venal.
2.
hired to serve in a foreign army, guerrilla organization, etc.
–noun
3.
a professional soldier hired to serve in a foreign army.
4.
any hireling.
Origin: 1350–1400; ME mercenarie < L mercēnnārius working for pay, hired worker, mercenary, perh., repr. earlier *mercēd(i)nārius, equiv. to *mercēdin-, s. of *mercēdō, a by-form of mercēs, s. mercēd- payment, wage (akin to merx goods; cf. merchant) + -ārius-ary
c.1386, "one who works only for hire," from L. mercenarius "one who does anything for pay," lit. "hired, paid," from merces (gen. mercedis) "pay, reward, wages," from merx (see market). The adj. is recorded from 1532.