aggressor Meaning, Definition & Usage

  1. noun someone who attacks
    attacker; assailant; assaulter.
  2. noun a confident assertive person who acts as instigator

WordNet

Ag*gres"sor noun
Etymology
L.: cf. F. agresseur.
Definitions
  1. The person who first attacks or makes an aggression; he who begins hostility or a quarrel; an assailant.
    The insolence of the aggressor is usually proportioned to the tameness of the sufferer. Ames.

Webster 1913