Is there a noun called a inproper noun?

Answer 1

An 'improper noun' is usually called a 'common noun'. A common noun is a word for a person, place, or thing in general; for example neighbor, town, or lunch.

Answer 2

There is no grammatical category called "inproper noun." Nouns are typically categorized as common or proper based on their capitalization, with proper nouns referring to specific names of people, places, or things. Please double-check if you meant something different.