OCCASIONAL, adj. Afflicting us with greater or less frequency. That,
however, is not the sense in which the word is used in the phrase
"occasional verses," which are verses written for an "occasion," such
as an anniversary, a celebration or other event. True, they afflict
us a little worse than other sorts of verse, but their name has no
reference to irregular recurrence.
-- Ambrose Bierce, "The Devil's Dictionary"
OBSOLETE, adj. No longer used by the timid. Said chiefly of words.
A word which some lexicographer has marked obsolete is ever thereafter
an object of dread and loathing to the fool writer, but if it is a
good word and has no exact modern equivalent equally good, it is good
enough for the good writer....