The acronym "thm" stands for "theorem", and there are several synonyms that could be used in its place. One such synonym is "axiom", which refers to a statement or proposition that is considered self-evidently true. Another synonym for "theorem" is "postulate", which is a fundamental assumption that serves as a basis for further reasoning. "Lemma" is another synonym that refers to a smaller proposition that is used to prove a larger one. Other similar words that could be used in place of "theorem" include "proposition", "corollary", and "formula". These terms all refer to ideas or statements that have been proven or established within a given field of study.