actually there is no such term Ultra is Latin and means (beyond) as in Ultra-Violet. In the context it might mean extremely orthodox ( doctrinally speaking) Catholics who might advocated a return to the Latin Liturgy, a turn-around of such things as alleged ( Audience participation) in the mass in favor of more worshipful attitudes, and so on. actually, I have never heard this term used and I used to write articles for ( and regularily read) the now defunct SIGN magazine.