WordRel.com

• (biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction

  domain topic	biochemistry
  hypernym	drug

• a muscle that contracts while another relaxes

  hypernym

  antagonistic muscle

• someone involved in a contest or battle (as in an agon)

  antonym	antagonist
  derivation	agonisticagonyagony
  hypernym	contestant

• the principal character in a work of fiction

  synonym	protagonist
  derivation	agony
  hypernym	characterfictional characterfictitious character
  hyponym	antihero