D defs.my
Entry 1 sense Webster, 1913

Aggressor

/əg-rĕs'-ẽr/ · Ag·gres·sor · IPA /əˈɡɹɛsɚ/
01 n. The person who first attacks or makes an aggression; he who begins hostility or a quarrel; an assailant.
  1. 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.