Noah Webster's Dictionary (n.) A captain, leader, or commander; a chief; the head of a troop, army, or clan.

Multi-Version Concordance Chieftain (2 Occurrences) 1 Chronicles 5:6 Beerah his son, whom Tiglath-pileser, king of Assyria, took away as a prisoner: he was chief of the Reubenites. (See RSV) Zechariah 9:7 I will take away his blood out of his mouth, and his abominations from between his teeth; and he also will be a remnant for our God; and he will be as a chieftain in Judah, and Ekron as a Jebusite. (WEB ASV)