Yes, worst is a Scrabble word!

Adverb

1. To the highest degree of inferiority or badness

Verb

1. Defeat thoroughly

Adjective

1. (superlative of `bad') most wanting in quality or value or condition

2. Having undesirable or negative qualities

3. Very intense

4. Feeling physical discomfort or pain (`tough' is occasionally used colloquially for `bad')

5. (of foodstuffs) not in an edible or usable condition

6. Feeling or expressing regret or sorrow or a sense of loss over something done or undone

7. Not capable of being collected

8. Below average in quality or performance

9. Nonstandard

10. Not financially safe or secure

11. Physically unsound or diseased

12. Capable of harming

13. Characterized by wickedness or immorality

14. Reproduced fraudulently

15. Not working properly

Noun

1. The least favorable outcome

2. The greatest damage or wickedness of which one is capable

3. The weakest effort or poorest achievement one is capable of