Is Indian an adjective for corn?

The Word corn (plant or food) is a noun. A related adjective is corn-like (corny having an entirely different meaning).

Used with other nouns, corn is a noun adjunct, or attributive noun (e.g. corn crop, corn flakes).

There is a verb, to corn, meaning to treat with rock salt, and it has the participle adjective form corned (corned beef).