The Collaborative International Dictionary
Supervacaneous
Supervacaneous \Su`per*va*ca"ne*ous\, a. [L. supervacaneus,
supervacuus; super over + vacuus empty.]
Serving no purpose; superfluous; needless. [Obs.]
--Howell.
Wiktionary
supervacaneous
a. (context now rare English) added above what is (l en needed) or (l en necessary); (l en superfluous), (l en redundant).