crispen vs crisp

crispen is not a noun while crisp is a noun.

Word	Noun	Adjective	Verb	Adverb
crispen	No	No	Yes	No
crisp	Yes	Yes	Yes	No

As verbs, crispen and crisp are synonyms defined as:

Other synonyms of crispen include toast.

crispen (noun)	crisp (noun)
	a thin crisp slice of potato fried in deep fat

crispen (adjective)	crisp (adjective)
	pleasantly cold and invigorating
	brief and to the point; effectively cut short
	(of hair) in small tight curls
	(of something seen or heard) clearly defined
	pleasingly firm and fresh
	tender and brittle

crispen (verb)	crisp (verb)
make brown and crisp by heating	make brown and crisp by heating
	make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic