It is the body of+teachings of a Pope or bishop. It can also be on a subject. The Church's Magisterium on Contraception is inconsistent with science, specifically on contraception and evolution, mostly because they have refused to take into account that knowledge of gastrulation allows one to follow moral caution about when life begins or does not begin vis-a-vis conception (doubt is removed, the moral principle is the extent to which you must be certain, understanding gastrulation provides that certainty). On evolution, the science is overwhelming and rejectionism is not the answer and so is Pius XII's counteroffer on first parents. In both cases, it is organizational pathology, the certainty that conflicting facts are false, that is toxic. It is a sign of stubbornness, not faith. What they should do is go back to the text and understand that the author was teaching a moral, not history. Original sin becomes a flaw in the human condition rather than inherited disobedience.