If you describe something as unnatural, you mean that it is strange and often frightening, because it is different from what you normally expect. The aircraft rose with unnatural speed on take-off The altered landscape looks unnatural and weird. + unnaturally un·natu·ral·ly The house was unnaturally silent. unnaturally cold conditions
not in accordance with or determined by nature; contrary to nature; "an unnatural death"; "the child's unnatural interest in death
Not natural; contrary, or not conforming, to the order of nature; being without natural traits; as, unnatural crimes
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"
not in accordance with or determined by nature; contrary to nature; "an unnatural death"; "the child's unnatural interest in death"
Behaviour that is unnatural seems artificial and not normal or genuine. She gave him a bright, determined smile which seemed unnatural. = false + unnaturally un·natu·ral·ly Try to avoid shouting or speaking unnaturally