Plain

1. Flat, level, mostly treeless. The plains of Texas are vast.
2. Ordinary; lacking adornment or ornamentation; unembellished. She wore a plain grey dress.
3. Downright; total, unmistakable. Her answer was just plain nonsense.
4. Honest and without deception; candid, open; blunt. Let me be plain with you. I don't like him.
5. Simple in habits or qualities; unsophisticated, not exceptional, ordinary. They're just plain folks like you and me.
6. Simply. That's just plain stupid.
7. (of food) Having only a few ingredients, or no additional ingredients or seasoning; not elaborate, without toppings or extras. Do you like your coffee plain?