[very common; orig. {Unix}] A program that processes an input data
stream into an output data stream in some well-defined way, and does
no I/O to anywhere else except possibly on error conditions; one
designed to be used as a stage in a pipeline (see {plumbing}).
Compare {sponge}.
[glossary]
[Reference(s) to this entry by made by: {special-case}{sponge}{tool}]