WordNet (r) 3.0 (2006):

Esther
    n 1: (Old Testament) a beautiful Jewess chosen by the king of
         Persia to be his queen; she stopped a plot to massacre all
         the Jews in Persia (an event celebrated by Jews as the
         feast of Purim)
    2: an Old Testament book telling of a beautiful Jewess who
       became queen of Persia and saved her people from massacre
       [syn: Esther, Book of Esther]

Easton's 1897 Bible Dictionary:

Esther
   the queen of Ahasuerus, and heroine of the book that bears her
   name. She was a Jewess named Hadas'sah (the myrtle), but when
   she entered the royal harem she received the name by which she
   henceforth became known (Esther 2:7). It is a Syro-Arabian
   modification of the Persian word satarah, which means a star.
   She was the daughter of Abihail, a Benjamite. Her family did not
   avail themselves of the permission granted by Cyrus to the
   exiles to return to Jerusalem; and she resided with her cousin
   Mordecai, who held some office in the household of the Persian
   king at "Shushan in the palace." Ahasuerus having divorced
   Vashti, chose Esther to be his wife. Soon after this he gave
   Haman the Agagite, his prime minister, power and authority to
   kill and extirpate all the Jews throughout the Persian empire.
   By the interposition of Esther this terrible catastrophe was
   averted. Haman was hanged on the gallows he had intended for
   Mordecai (Esther 7); and the Jews established an annual feast,
   the feast of Purim (q.v.), in memory of their wonderful
   deliverance. This took place about fifty-two years after the
   Return, the year of the great battles of Plataea and Mycale
   (B.C. 479).

     Esther appears in the Bible as a "woman of deep piety, faith,
   courage, patriotism, and caution, combined with resolution; a
   dutiful daughter to her adopted father, docile and obedient to
   his counsels, and anxious to share the king's favour with him
   for the good of the Jewish people. There must have been a
   singular grace and charm in her aspect and manners, since 'she
   obtained favour in the sight of all them that looked upon her'
   (Esther 2:15). That she was raised up as an instrument in the
   hand of God to avert the destruction of the Jewish people, and
   to afford them protection and forward their wealth and peace in
   their captivity, is also manifest from the Scripture account."


Hitchcock's Bible Names Dictionary (late 1800's):

Esther, secret; hidden