a-'dar ('adhar, meaning uncertain): The Babylonian name of the twelfth month of the year. Used in the Bible only in Ezr 6:15 and eight times in Esther. At first the author in Esther defines Adar as the twelfth month, but afterward omits the numeral. In order to maintain the relation of the year to the seasons it was customary to add a second Adar, as often as was needed, as an intercalary month.
⇒See a list of verses on ADAR in the Bible.