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,
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.