|Easton's Bible Dictionary|
One of the eunuchs who "kept the door" in the court of Ahasuerus. With Teresh he conspired against the king's life. Mordecai detected the conspiracy, and the culprits were hanged (Esther 2:21-23; 6:1-3).
Int. Standard Bible Encyclopedia
big'-than big-tha'-na (bighethan, bighethana'; Septuagint omits name): One of the two chamberlains or eunuchs of Xerxes on ("Ahasuerus") who conspired against the king's life, the conspiracy being detected by Mordecai and the culprits hanged (Esther 2:21). Possibly these men had been partially superseded by the degradation of Vashti and were thus prompted to take revenge Xerxes.
Bigthan (1 Occurrence)
Esther 2:21 In those days, while Mordecai was sitting in the king's gate, two of the king's eunuchs, Bigthan and Teresh, who were doorkeepers, were angry, and sought to lay hands on the King Ahasuerus. (WEB KJV JPS ASV BBE DBY WBS YLT NAS RSV NIV)