I am indebted to Robert Carter for suggesting this alternative. On reflection, I think it would be preferable here to my first suggestion, "landed nobility", so with Robert's encouragement I offer it as an alternative.

I think it is clear that "señorial" refers to possessing and exercising "señorío", which means, in the words of the article I cited in my first answer, "dominación sobre tierras y hombres". Landed estates are estates that generate income, through rents of various kinds. This is one of the bases of feudalism. Indeed, it would not be altogether inaccurate to translate this term as "feudal nobility". However, the word "feudal" is really associated with the medieval period, and by the early modern period (starting in the late fifteenth century) the social system underlying feudalsim in the strict sense was changing, so the word "feudal" is to some extent an anachronism: the medieval vassal-lord relationship was evolving into something a bit different; the theory underlying the feudal system of rights and mutual obligations

It is customary among English-speaking historians of Spain to refer to the higher nobles who held estates in the early modern period as "seigneurial", and I think that is how "señorial" is being used here. Although it is accurate to call them "landed" nobles, I think "seigneurial" captures the full implications of "señorial" better: not just possession of land but the economic control over people, now tenants rather than strictly vassals in the old sense. This is particularly true of Andalusia, where the system of large estates or latifundios was perpetuated.

Some examples of "seigneurial nobility" in relation to Spain. The following, by Brian Hamnett (Emeritus Profesor of History at Essex University), is about the eighteenth century, underlining the perpetuation of the seigneurial system in Spain, as in France, right up to the French Revolution (1812 in the case of Spain):

"Bringing new talent, often from provincial and lesser nobilities, into ministerial positions did not affect the continuing social dominance of the seigneurial nobility, civil or ecclesiastical, beyond immediate court circles."
https://books.google.es/books?id=X81RDwAAQBAJ&pg=PT135&lpg=P...

"Up until 1812 the class of great landowners formally constituted the seigneurial nobility"
Carlos Marichal, Spain, 1834-1844: A New Society
https://books.google.es/books?id=GIM1sxP8XBAC&pg=PA12
(Marichal is Mexican but he studied at Harvard and his English is perfectly reliable.)

And a number of references to the "seigneurial" system in Spain can be found in the work of reliable historians. I think it's suitable here.