/pes'im-l/ (Latin-based antonym for "optimal") Maximally bad.
"This is a pessimal situation." Also "pessimise" To make as
bad as possible. These words are the obvious Latin-based
antonyms for "optimal" and "optimise", but for some reason
they do not appear in most English dictionaries, although
"pessimise" is listed in the OED.
(1995-02-01)