acetate

Short definition from Wiktionary

Noun

1. 1
   Any ester or salt of acetic acid.
2. 2
   Cellulose acetate.
3. 3
   A transparent sheet used for overlays, whether of cellulose acetate or (loosely) any macroscopically similar plastic.
4. 4
   In full acetate disc: a disc of aluminium covered in a wax used to make demonstration copies of a phonograph record.