The Collaborative International Dictionary of English v.0.48:

Aggress \Ag*gress"\, v. t.
   To set upon; to attack. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Aggress \Ag*gress"\, n. [L. aggressus.]
   Aggression. [Obs.]
   [1913 Webster]

         Their military aggresses on others.      --Sir M. Hale.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Aggress \Ag*gress"\, v. i. [imp. & p. p. Aggressed; p. pr. &
   vb. n. Aggressing.] [L. aggressus, p. p. of aggredi to go
   to, approach; ad + gradi to step, go, gradus step: cf. OF.
   aggresser. See Grade.]
   To commit the first act of hostility or offense; to begin a
   quarrel or controversy; to make an attack; -- with on.
   [1913 Webster]

   2. take the initiative and go on the offensive, as in a game.

   Syn: attack
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

aggress
    v 1: take the initiative and go on the offensive; "The Serbs
         attacked the village at night"; "The visiting team started
         to attack" [syn: attack, aggress]