Boyd’s Bible Dictionary:

(little). A Benjamite captive at court of Ahasuerus, and deliverer of Jews from plot of Haman (Esther).

Concise Bible Dictionary:

2. A Benjamite, first cousin of Esther, queen of Ahasuerus, who, being an orphan, had been brought up by him. All that is known of his history is contained in the book of Esther. Though a captive he had liberty to sit at the gate of the palace, and when Haman was promoted, the faith of Mordecai shines out in that he refused to bow to Haman an Agagite, even at the command of the king. His reason is not given, but it was doubtless because Haman was an Amalekite, upon whom the curse of God rested. Saul was told to utterly destroy them, even to the asses (Ex. 17:14,1614And the Lord said unto Moses, Write this for a memorial in a book, and rehearse it in the ears of Joshua: for I will utterly put out the remembrance of Amalek from under heaven. (Exodus 17:14)
16For he said, Because the Lord hath sworn that the Lord will have war with Amalek from generation to generation. (Exodus 17:16)
; Deut. 25:1919Therefore it shall be, when the Lord thy God hath given thee rest from all thine enemies round about, in the land which the Lord thy God giveth thee for an inheritance to possess it, that thou shalt blot out the remembrance of Amalek from under heaven; thou shalt not forget it. (Deuteronomy 25:19); 1 Sam. 15:33Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass. (1 Samuel 15:3)). Mordecai, by this action, put his life in danger because of the position of Haman; but, though warned, he was staunch in his refusal.
This led to Haman’s plotting in his pride, the destruction, not of Mordecai only, but of the Jews generally. God, however, was watching over His people, and when the right moment came, He wrought deliverance. He caused that the king should not sleep, and that the records should be read to him, which brought Mordecai’s unrequited service to remembrance. The proud Agagite had to lead him, seated on the king’s horse, through the city, and proclaim him as one whom the king delighted to honor. The fall of Haman rapidly followed, and the raising of Mordecai into power. Thus did God honor the faith of one of His people, though they were in captivity. The plot against the Jews was nullified and they became the victors, as it will be in a future day when God’s set time has arrived. Mordecai was promoted to high honor and was next to the king; he sought the wealth of his people, “speaking peace to all his seed.”

Strong’s Dictionary of Hebrew Words:

of foreign derivation; Mordecai, an Israelite
KJV Usage:

Jackson’s Dictionary of Scripture Proper Names:

bitterness of my oppressed

Potts’ Bible Proper Names:

Taught of God; contrition; little man:―a Benjamite captive, Esth. 2:5. {Doctus a Domino}