Not having been washed. / Vulgar, plebeian, lowbrow.

Something that cannot be washed in the normal way without being damaged.

Not washable; that cannot be washed.

plural of unwashable

(idiomatic, derogatory) The general populace, particularly the working class.

(derogatory) The collective group of people who are considered to be uneducated, uninformed, or in some other way unqualified for inclusion in the speaker's elite circles.

The property of being unwashed.