- unnatural - not in accordance with or determined by nature; contrary to nature; "an unnatural death"; "the child's unnatural interest in death"
Antonyms: natural, earthy, elemental
- affected, unnatural - speaking or behaving in an artificial way to make an impression
- grotesque, monstrous, unnatural - distorted and unnatural in shape or size; abnormal and hideous; "tales of grotesque serpents eight fathoms long that churned the seas"; "twisted into monstrous shapes"
Antonym: beautiful (indirect, via ugly)