The Collaborative International Dictionary of English v.0.48:

Algebraic \Al`ge*bra"ic\, Algebraical \Al`ge*bra"ic*al\, a.
   1. Of or pertaining to algebra; using algebra; according to
      the laws of algebra; containing an operation of algebra,
      or deduced from such operation; as, algebraic characters;
      algebraical writings; algebraic geometry.
      [1913 Webster]

   2. progressing by constant multiplicatory factors; -- of a
      series of numbers. Contrasted to arithmetical. algebraic
      progression

   Syn: algebraic
        [PJC]

   Algebraic curve, a curve such that the equation which
      expresses the relation between the co["o]rdinates of its
      points involves only the ordinary operations of algebra;
      -- opposed to a transcendental curve.
      [1913 Webster]

WordNet (r) 3.0 (2006):

algebraical
    adj 1: of or relating to algebra; "algebraic geometry" [syn:
           algebraic, algebraical]