Yes, is is a Scrabble word!
...and is worth 2 points in Scrabble, and 2 points in Words with Friends
is
Verb
1. Have the quality of being; (copula, used with an adjective or a predicate noun)
2. Be identical to; be someone or something
3. Occupy a certain position or area; be somewhere
4. Have an existence, be extant
5. Happen, occur, take place; this was during the visit to my parents' house"
6. Be identical or equivalent to
7. Form or compose
8. Work in a specific place, with a specific subject, or in a specific function
9. Represent, as of a character on stage
10. Spend or use time
11. Have life, be alive
12. To remain unmolested, undisturbed, or uninterrupted -- used only in infinitive form
13. Be priced at
What Scrabble words can I make with the letters in is?
2 Letter Words