mACF (short for "mock-ACF" or "modified-ACF") is a term applied to academic tournaments that follow the ACF format without being official ACF events.
As ACF tournaments do not include powers, the term "mACF" often refers to tournaments that use twenty untimed tossups and bonuses with powers. However, since the joint ACF/PACE common ruleset project before the 2016-2017 season, the ACF rules now include an "optional powermark addendum," meaning that these tournaments do not actually modify the existing ACF rules.
Usefulness of term
The term was used more often in the early and mid-2000s, when college and high-school tournaments were more likely to imitate CBI or bad local formats. Since every full-length tournament in collegiate quizbowl besides NAQT ICT uses an untimed tossup/bonus format, and most use questions that are closer to ACF style than NAQT's, it is unclear what helpful information is communicated by dubbing a collegiate tournament mACF as opposed to not doing so. It is generally more effective to give a more detailed description of the intended length and difficulty standards of one's tournament (e.g. "7-line tossups, difficulty akin to ACF Regionals 2010"), and more tournament announcements have done so since the early 2010s, leaving the term "mACF" behind.
More recently, the term has seen a resurgence of usage among the high-school quizbowl community, to distinguish sets with an ACF-like subject distribution (including PACE NSC and most housewrites) from NAQT sets. Since 2018–19, GrogerRanks has released a set of "mACF-only" rankings (along with a set of "NAQT-only" rankings) before each year's midseason and pre-nationals polls, and after each year's nationals.