Any adjective that is not gradable.
That cannot be graded.
(of an adjective) Describing a quality that cannot normally be varied because it is extreme (e.g. freezing), absolute (e.g. dead), or classification (e.g. nuclear).
A person or thing of distinction.
Worthy of note; remarkable; memorable; noted or distinguished.
Easily noted (without connotations of value); clearly noticeable, conspicuous.
That can be observed; perceptible.