n.
   - a large, ugly, and frightening imaginary creature. ▸an inhumanly cruel or wicked person. ▸humorous a rude or badly behaved child. 
- a congenitally malformed or mutant animal or plant.
- 
[as modifier]
 informal extraordinarily large.
v.
 Brit. informal criticize severely.
Etymology
  ME: from OFr. monstre, from L. monstrum ‘portent or monster’, from monere ‘warn’.