Middle English, from Old French monstruos, from Latin mōnstruōsus, from mōnstrum, portent, monster.

1. Shockingly hideous or frightful.
2. Exceptionally large; enormous: a monstrous tidal wave.
3. Deviating greatly from the norm in appearance or structure; abnormal.
4. Of or resembling a fabulous monster.

Related to the idea of "grotesque" is the idea of the "monstrous", which is defined in Collins as "abnormal, hideous, or unnatural" . Rosi Braidotti points out: "The monster is the bodily incarnation of difference from the basic human norm; it is a deviant, an a-nomaly, it is abnormal... the very notion of the human body rests upon an image that is intrinsically prescriptive: a normally formed human being is the zero-degree of monstrosity.

 Synonyms

aberrant, abnormal, atrocious, behemoth, Brobdingnagian, Bunyanesque, colossal, cruel, cyclopean, desperate, devilish, diabolical, disgraceful, dreadful, egregious, elephantine, enormous, evil, fiendish, flagitious, foul, frightful, freakish, freaky, gargantuan, giant, gigantesque, gigantic, grotesque, gruesome, herculean, heinous, hellish, hideous, horrendous, horrible, horrifying, heroic, huge, immense, incredible, infamous, inhuman, intolerable, jumbo, macabre, mammoth, massive, massy, mastodonic, mighty, miscreated, monster, monumental, mountainous, morbid, obscene, odious, ominous, outrageous, preposterous, prodigious, pythonic, satanic, scandalous, shocking, spooky, stupendous, teratoid, terrible, titanic, tremendous, unusual, uncanny, vicious, villainous, whopping,