1. [n]  verse in which certain letters such as the first in each line form a word or message
2. [n]  a puzzle where you fill a square grid with words reading the same down as across

ACROSTIC is a 8 letter word that starts with A.

1. \A*cros"tic\, n. [Gr. ?; ? extreme + ? order, line,
   verse.]
   1. A composition, usually in verse, in which the first or the
      last letters of the lines, or certain other letters, taken
      in order, form a name, word, phrase, or motto.
   2. A Hebrew poem in which the lines or stanzas begin with the
      letters of the alphabet in regular order (as Psalm cxix.).
      See {Abecedarian}.
   {Double acrostic}, a species of enigma
   

2. \A*cros"tic\, Acrostical \A*cros"tic*al\, n.
   Pertaining to, or characterized by, acrostics.