Swap \Swap\, v. t. [imp. & p. p. Swapped; p. pr. & vb. n. Swapping.]

[OE. swappen to strike; cf. E. to strike a bargain; perh. akin to E. sweep. Cf. Swap a blow, Swap, v. i.]

[Written also swop.]

1. To strike; -- with off. [Obs. or Prov. Eng.]

``Swap off his head!'' --Chaucer.

2. To exchange (usually two things of the same kind); to swop. [Colloq.]

--Miss Edgeworth.

Source: Webster's Revised Unabridged Dictionary (1913)