cobwebby vs gossamer

cobwebby is not a noun while gossamer is a noun.

Word	Noun	Adjective	Verb	Adverb
cobwebby	No	Yes	No	No
gossamer	Yes	Yes	No	No

As adjectives, cobwebby and gossamer are synonyms defined as:

Other synonyms of cobwebby include diaphanous, filmy, gauze-like, gauzy, see-through, sheer, transparent, vaporous, vapourous.

cobwebby (noun)	gossamer (noun)
	a gauze fabric with an extremely fine texture
	filaments from a web that was spun by a spider

cobwebby (adjective)	gossamer (adjective)
covered with cobwebs	characterized by unusual lightness and delicacy
so thin as to transmit light	so thin as to transmit light