Is skirt a proper noun

Yes, the Word 'skirt' is both a verb and a noun.

The noun 'skirt' is a Word for a type of garment fastened around the waist that hangs down around the waist; a Word for an attachment serving as a rim, border, or edging; a Word for a thing.

The verb 'skirt' is to move along the edge of something or to go around something; a Word for an action.