A true alien, that is, a member of a species unknown to us both.

They look for many different kinds of fish, both known and unknown species.

He identified at least four species previously unknown in Nigeria.

They're under attack by some unknown alien species and need help desperately.

Among the collection were 500 species previously unknown to science (Davis 2000).

It is possible that this unknown alien species captured him.

He discovered and named more than 30 previously unknown species.

It depicts a herb of unknown species in a red color.

You can't be sure of reactions in an unknown species.

She looked at them as if they were an unknown species.