Wafer

A thin cake made of fine flour, Exodus 16:31, and used in carious offerings, anointed with sweet oil, Exodus 29:2,23; Leviticus 2:4; 7:12; Numbers 6:15.

Source: ATS Bible Dictionary
Wafer

WAFER, n.

1. A thin cake or leaf; as a wafer of bread given by the Romanists in the Eucharist.
2. A thin leaf of paste, or a composition of flour, the white of eggs, isinglass and yeast, spread over with gumwater and dried; used in sealing letters.

WAFER, v.t. To seal or close with a wafer.

Source: King James Dictionary