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

Not washable; that cannot be washed.

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

plural of unwashable

(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.

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

The property of being unwashed.