1. [n]  a word or phrase spelled by rearranging the letters of another word or phrase
2. [v]  read letters out of order to discover a hidden meaning

ANAGRAM is a 7 letter word that starts with A.

1. \An"a*gram\, n. [F. anagramme, LL. anagramma, fr. Gr. ?
   back, again + ? to write. See {Graphic}.]
   Literally, the letters of a word read backwards, but in its
   usual wider sense, the change or one word or phrase into
   another by the transposition of its letters. Thus Galenus
   becomes angelus; William Noy (attorney-general to Charles I.,
   and a laborious man) may be turned into I moyl in law.
   

2. \An"a*gram\, v. t.
   To anagrammatize.
         Some of these anagramed his name, Benlowes, into
         Benevolus.                               --Warburton.