:TOPS-10:: /tops-ten/ n. DEC's proprietary OS for the fabled {PDP-10}
machines, long a favorite of hackers but now effectively extinct.
A fountain of hacker folklore; see {Appendix A}. See also {{ITS}},
{{TOPS-20}}, {{TWENEX}}, {VMS}, {operating system}. TOPS-10 was
sometimes called BOTS-10 (from `bottoms-ten') as a comment on the
inappropriateness of describing it as the top of anything.
-- The AI Hackers Dictionary