Rambam, Mishneh Torah 3:7.
“Five individuals are described as Minim:
a) one who says there is no God nor ruler of the world;
b) one who accepts the concept of a ruler, but maintains that there are two or more;
c) one who accepts that there is one Master [of the world], but maintains that He has a body or form;
d) one who maintains that He was not the sole First Being and Creator of all existence;
e) one who serves a star, constellation, or other entity so that it will serve as an intermediary between him and the eternal Lord.”
Nothing about disputing Chazal here, either. (b), (c), (d), and possibly (e) appear to refer to Christians.