1. in a way that is not normal or natural; artificially or strangely
2. to an extreme or excessive degree

Examples

• Her smile looked unnaturally bright in the photograph.
• The room was unnaturally quiet after the announcement.
• He spoke in an unnaturally high voice when he was nervous.
• The flowers had been dyed an unnaturally vivid blue.
• She was unnaturally calm during the crisis.
• The lake’s water glowed unnaturally green under the lights.
• His hair was unnaturally perfect, clearly styled with gel.