She received an unnamed gift.

The horror that lurked in the shadows was unnameable.

The creature lurking in the shadows was unnamable.

The unnamableness of the situation made it difficult to find a solution.

The unnamability of the creature made it even more mysterious.

The unnameability of the experience left her speechless.

She danced unnamably across the stage.

She danced unnameably across the stage, her movements defying description.

The unnameableness of the experience left me speechless.

She unnames her cat every time she gets a new one.