From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

A Gibeonite chief of the men who left Saul, the head of their tribe, to join David at Ziklag ( 1 Chronicles 12:1-4); "a mighty man among the 30 and over the 30."

Morrish Bible Dictionary [2]

A Gibeonite, the head of David's thirty valiant men: he joined David at Ziklag.  1 Chronicles 12:4 .

Holman Bible Dictionary [3]