'un-' is a prefix to nouns, adjectives, and secondary adverbs, and is generally purely negative, though sometimes intensitive in the sense of 'bad': […]

The legendary Bigfoot is said to be a manlike creature.

Mostly we heard her laughing and the squeaking of the porch swing while the boyfriend felt her up. All the boys went to second base with Diana Estabrook.

In a drab first half, Ryan Shotton's drive was deflected on to a post and Jon Walters twice went close.