What does "monster" mean?

Monster: Specifically , an animal or plant departing greatly from the usual type, as by having too many limbs.

Additional senses

  1. 2.Any thing or person of unnatural or excessive ugliness, deformity, wickedness, or cruelty.
  2. 3.Monstrous in size. Pope.
  3. 4.To make monstrous. [Obs.] Shak.

Sources