Literally meaning "to this", ad hoc is used to indicate that something happens for a single purpose only.
e.g. "The Bursar formed an ad hoc committee to look at the site's security problems."
Abbreviated: a.m. & p.m., cf., e.g., et al., etc., i.e., N.B., P.S., Q.E.D., q.v., viz.
Non abbreviated: ad hoc, de facto, modus operandi, non sequitur, pro rata, quid pro quo, sic, vice versa.