The Collaborative International Dictionary of English v.0.48:

Nisan \Ni"san\, n. [Heb. n[imac]s[=a]n.]
   The first month of the Jewish ecclesiastical year, formerly
   answering nearly to the month of April, now to March, of the
   Christian calendar. See Abib.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Abib \A"bib\, n. [Heb. ab[imac]b, lit. an ear of corn. The month
   was so called from barley being at that time in ear.]
   The first month of the Jewish ecclesiastical year,
   corresponding nearly to our April. After the Babylonish
   captivity this month was called Nisan. --Kitto.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Nisan
    n 1: the seventh month of the civil year; the first month of the
         ecclesiastic year (in March and April) [syn: Nisan,
         Nissan]

Easton's 1897 Bible Dictionary:

Nisan
   month of flowers, (Neh. 2:1) the first month of the Jewish
   sacred year. (See ABIB.) Assyrian nisannu,
   "beginning."


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

Nisan, standard; miracle