Yes, giant is a Scrabble word!

Adjective

1. Of great mass; huge and bulky

Noun

1. Any creature of exceptional size

2. A person of exceptional importance and reputation

3. An unusually large enterprise

4. A very large person; impressive in size or qualities

5. Someone or something that is abnormally large and powerful

6. An imaginary figure of superhuman size and strength; appears in folklore and fairy tales

7. A very bright star of large diameter and low density (relative to the Sun)