Exes.

A lot of people bandy about the term "ex-priest" to describe a man who once received Holy Orders and since has been officially removed from clerical activities — that is, "laicized" (the correct, general, and non-derogatory term) or "defrocked" (a term which implies a punitive laicization). 

"Ex-priest" is technically not correct in Catholic understanding.  We believe that Holy Orders, like baptism, forms an "indelible mark on the soul" — that a priest validly ordained is a priest forever.  Indeed, priesthood survives death, unlike that other nuptial state of being, matrimony.   So it isn’t surprising that even a laicized priest is bound by some rules that non-priests aren’t.  Jimmy Akin, ever a fount of interesting and detailed tidbits, has the story.

The restrictions aren’t just about administering the sacraments.  They also cover things like serving in leadership roles in parishes and Catholic universities, and even teaching theology in non-Catholic universities.  One thing I didn’t know about laicization is that, although many of the restrictions are generally applicable, in practice each laicized priest receives an individual, personally tailored list of restrictions. 

Also interesting is the fact that being laicized doesn’t automatically release a priest from celibacy — he isn’t automatically free to marry.  It is possible for a laicized priest to receive a dispensation from priestly celibacy, but that appears to be a second, separate decision.