Yes, cap is a Scrabble word!

Verb

1. Lie at the top of

2. Restrict the number or amount of

Noun

1. A tight-fitting headdress

2. A top (as for a bottle)

3. A mechanical or electrical explosive device or a small amount of explosive; can be used to initiate the reaction of a disrupting explosive

4. Something serving as a cover or protection

5. A fruiting structure resembling an umbrella or a cone that forms the top of a stalked fleshy fungus such as a mushroom

6. A protective covering that is part of a plant

7. An upper limit on what is allowed

8. (dentistry) dental appliance consisting of an artificial crown for a broken or decayed tooth

9. The upper part of a column that supports the entablature