Webster's Revised Unabridged Dictionary · 1913

Wafer

Wafer , noun

[Old English wafre, Old French waufre, qaufre, French qaufre; of Teutonic origin; compare LG. & Dutch wafel, German waffel, Danish vaffel, Swedish våffla; all akin to German wabe a honeycomb, Old High German waba, being named from the resemblance to a honeycomb. German wabe is probably akin to English weave. See Weave, and compare Waffle, Gauffer.]

1.
(Cookery) A thin cake made of flour and other ingredients.
Wafers piping hot out of the gleed. — Chaucer
The curious work in pastry, the fine cakes, wafers, and marchpanes. — Holland
A woman's oaths are wafers -- break with making — B. Jonson
2.
(Ecclesiastical) A thin cake or piece of bread (commonly unleavened, circular, and stamped with a crucifix or with the sacred monogram) used in the Eucharist, as in the Roman Catholic Church.
3.
An adhesive disk of dried paste, made of flour, gelatin, isinglass, or the like, and coloring matter, -- used in sealing letters and other documents.
4.
Any thin but rigid plate of solid material, esp. of discoidal shape; -- a term used commonly to refer to the thin slices of silicon used as starting material for the manufacture of integrated circuits.
Collocations (3)
Wafer cake , a sweet, thin cake. — Shakespeare
Wafer irons or Wafer tongs (Cookery) , a pincher-shaped contrivance, having flat plates, or blades, between which wafers are baked.
Wafer woman , a woman who sold wafer cakes; also, one employed in amorous intrigues. — Beau. & Fl

Wafer , transitive verb

To seal or close with a wafer.