Yes, negative is a Scrabble word!

Verb

1. Vote against; refuse to endorse; refuse to assent

Adjective

1. Characterized by or displaying negation or denial or opposition or resistance; having no positive features

2. Expressing or consisting of a negation or refusal or denial

3. Having the quality of something harmful or unpleasant

4. Not indicating the presence of microorganisms or disease or a specific condition

5. Reckoned in a direction opposite to that regarded as positive

6. Less than zero

7. Designed or tending to discredit, especially without positive or helpful suggestions

8. Having a negative charge

9. Involving disadvantage or harm

Noun

1. A reply of denial

2. A piece of photographic film showing an image with light and shade or colors reversed