Prozymite

Whosever shall obstinately blame the faith of the Holy See of Rome and its sacrifices, let him be anathema, and let him not be deemed Catholic, but a prozymite heretic, that is to say, Defender of the Leaven.

The inclusion not only of [Michael I] Cerularius, but of all his followers, and the denunciation of the Greeks as prozymite heretics, does look like a condemnation of the whole Byzantine church until it should change its practices.

For example, Greeks using leavened bread for the consecration, were in opposition with the unleavened bread of the Latin Church, and stigmatised as fermentarians or prozymites.