wafer

Short definition from Wiktionary

Noun

1. 1
   A light, thin, flat biscuit/cookie.
2. 2
   A thin disk of consecrated unleavened bread used in communion.
3. 3
   A soft disk originally made of flour, and later of gelatin or a similar substance, used to seal letters, attach papers etc.
4. 4
   A thin disk of silicon or other semiconductor on which an electronic circuit is produced.

Verb

1. 1
   To seal or fasten with a wafer.