a thin, crisp cake or biscuit, often sweetened and flavored.

a thin disk of unleavened bread, used in the Eucharist, as in the Roman Catholic Church.

a thin disk of dried paste, gelatin, adhesive paper, or the like, used for sealing letters, attaching papers, etc.

Medicine/Medical . a thin sheet of dry paste or the like, used to enclose a powder to be swallowed.

any small, thin disk, as a washer or piece of insulation.

Electronics . a thin slice of semiconductor used as a base material on which single transistors or integrated-circuit components are formed.

to seal, close, or attach by means of a wafer or wafers

to wafer a letter.

noun

biscuit , cake , candy , cookie , cracker , disk