The word 'preform' is not a noun. The word 'preform' is a verb.
The verb 'preform' is to shape or form beforehand; to determine the shape or form of beforehand; a word for an action.
There are some dictionaries that designate the word 'preform' as a noun, a word for a something made or conceived before undergoing complete or final processing; a word for a thing.
The noun 'preform' is a common noun as a general word for any object or idea before completion or final processing.
The noun form of the verb to preform is the gerund, preforming.