The Free On-line Dictionary of Computing (30 December 2018):
1. To extract files from an archive
created with PKWare's PKZIP archiver.
2. A program to list, test, or extract
files from a ZIP archive, commonly found on MS-DOS
systems. zip, creates ZIP archives; both programs are
compatible with archives created by PKWARE, Inc.'s PKZIP
and PKUNZIP for MS-DOS.