Here it is used in a sentence
It is therefore a priori probable that Plato πυθαγοριζει in the passage where he says that between two planes one mean suffices, but to connect two solids, two means are necessary. - Sir Thomas Heath: A History of Greek Mathematics, Volume I: From Thales to Euclid, page 89
I realize this is not an equation question, but this forum might seems an appropriate place to ask a question about words used in discussions of number theory