[From the mnemonic for the PDP-11 ‘SWAp Byte’ instruction, as immortalized in the dd(1) option conv=swab (see dd)]

1. vt. To solve the NUXI problem by swapping bytes in a file

2. n. The program in V7 Unix used to perform this action, or anything functionally equivalent to it. See also big-endian, little-endian, middle-endian, bytesexual.