The square of a number. Now obsolete.
This word is actually doubly obsolete -- it's only remembered because of another obsolete word: zenzizenzizenzic.
Back when algebra was new to the Western world, there were some translation problems; for example, how did you translate the Arabic word mal? Today we would say "the square of a number"; back then they (the Italians) translated it to the medieval Italian word censo, meaning 'property' (as in the property of a number). This in turn was assimilated into German as zenzic, which was then taken into English without change.
By the 1500 there was still no good way to represent powers of numbers; the words 'square' and 'cube' were in use, as was 'zenzizenzic', from the Italian censo di censo, meaning fourth power (square of a square). The sixth power was zenzicube (square of a cube). The obvious extension, zenzizenzizenzic, was used by the Welsh-born mathematician Robert Recorde, in his book The Whetstone of Wit (1557), to mean an eighth power. It may have been used by others earlier, but apparently no record of this exists.
I cannot find when this word fell out of usage, but the modern method of writing exponents was first used by Descartes in 1637. This would have eliminated much of the need for words describing each power.
Now known only to mathematical historians and logomaniacs. And noders like yourself.