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
Best Answer
The verb is πυθαγορίζω (infinitive πυθαγορίζειν), formed by adding the derivative suffix -ιζω to the name of Pythagoras (Πυθαγόρας). So it just means "to be [or, in the context you quote, presumably, to act as] a disciple of Pythagoras"; or, to use an English equivalent, "to Pythagorize".
Sources:
The "Pythagorize" entry from Oxford Dictionaries (I'm not sure whether this coincides with the OED), which gives the etymology as "from ancient Greek Πυθαγορίζειν to be a disciple of Pythagoras from Πυθαγόρας, the name of Pythagoras + -ίζειν".
Perseus Greek word study tool [click on "LSJ"] translates it as "to be a disciple of Pythagoras", quoting uses: Antiph.226.8, Alex.220.1.
The entry for the suffix -ίζω in Wiktionary.