Yes, brooding is a Scrabble word!

Verb

1. Think moodily or anxiously about something

2. Hang over, as of something threatening, dark, or menacing

3. Be in a huff and display one's displeasure

4. Be in a huff; be silent or sullen

5. Sit on (eggs)

Adjective

1. Deeply or seriously thoughtful;

Noun

1. Sitting on eggs so as to hatch them by the warmth of the body

2. Persistent morbid meditation on a problem