Yes, harder is a Scrabble word!

Adverb

1. With effort or force or vigor

2. With firmness

3. Earnestly or intently

4. Causing great damage or hardship

5. Slowly and with difficulty

6. Indulging excessively

7. Into a solid condition

8. Very near or close in space or time

9. With pain or distress or bitterness

10. To the full extent possible; all the way

Adjective

1. Not easy; requiring great physical or mental effort to accomplish or comprehend or endure

2. Dispassionate;

3. Resisting weight or pressure

4. Very strong or vigorous

5. Characterized by effort to the point of exhaustion; especially physical effort

6. Produced without vibration of the vocal cords

7. (of light) transmitted directly from a pointed light source

8. (of speech sounds); produced with the back of the tongue raised toward or touching the velum

9. Given to excessive indulgence of bodily appetites especially for intoxicating liquors

10. Being distilled rather than fermented; having a high alcoholic content

11. Unfortunate or hard to bear

12. Dried out