Yes, slipes is a Scrabble word!

Verb

1. Move stealthily

2. Insert inconspicuously or quickly or quietly

3. Move obliquely or sideways, usually in an uncontrolled manner

4. Get worse

5. Move smoothly and easily

6. To make a mistake or be incorrect

7. Pass on stealthily

8. Move easily

9. Cause to move with a smooth or sliding motion

10. Pass out of one's memory

11. Move out of position