More accurately: Apikores = heretic in modern parlance; apikorsus = heretical views.

As an aside, Maimonides is the medieval Jewish authority generally associated with the view that the term apikores is not derived from the name Epicurus. Maimonides was a world-class Aristotelian philosopher and quotes Epicurus several times in his works. Since the words apikores and Epicurus have identical spellings in medieval Hebrew, the fact that Maimonides proposes a different etymological theory begs for an explanation. Maimonides' theory is that the term is from the Aramaic "apkeirusa" (this is hard to translate, especially in the way Maimonides seems to be using it; I think it implies something like "people doing whatever they feel like instead of listening to authority figures"). I've long felt that this derives from the fact that the Talmud's discussion of the term doesn't have anything to do with dogma or heretical beliefs but rather with belittling authority figures. Maimonides himself, however, converts the term in his other works into the current usage of referring to heretical beliefs. Based on this, I strongly suspect that Maimonides thought that the original term does stem from Epicurus (who held precisely those beliefs that Maimonides identifies as heretical), but that the rabbis of the Talmud borrowed the term and used it as a sort of Aramaic-Greek pun to refer to belittling authority figures.

Also in case anybody else is curious, Modern Orthodox is as opposed mainly to Ultra-Orthodox (also known as "hareidi" or "frum"). Hassidim are their own sub-group of Ultra-Orthodox.

As an interesting intellectual challenge, try steelmanning some of the hareidi sociopolitical positions, such as their extreme opposition to the Israeli draft law. And it does need steelmanning - I personally know several very well-thought-out, very smart, very well-meaning, very knowledgeable rabbis who strongly agree with the hareidi positions.