Adonijah

(1.) The fourth son of David (2 Sam. 3:4). After the death of his elder brothers, Amnon and Absalom, he became heir-apparent to the throne. But Solomon, a younger brother, was preferred to him. Adonijah, however, when his father was dying, caused himself to be proclaimed king. But Nathan[?] and Bathsheba induced David to give orders that Solomon should at once be proclaimed and admitted to the throne. Adonijah fled and took refuge at the altar, and received pardon for his conduct from Solomon on the condition that he showed himself "a worthy man" (1 Kings 1:5-53). He afterwards made a second attempt to gain the throne, but was seized and put to death (1 Kings 2:13-25).

(2.) A Levite sent with the princes to teach the book of the law to the inhabitants of Judah (2 Chr. 17:8).

(3.) One of the "chiefs of the people" after the Captivity[?] (Neh. 10:16).

From Easton's Bible Dictionary (1897)