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Retrograde accretion is that of an accretion disk rotating in the opposite direction from the accreting body's rotation. Whether retrograde or not, the rotation axes of the accreting body and the accretion disk can also be other than parallel.
A theory is that some central galaxy SMBH's are like this (retrograde accreting black holes, i.e., with retrograde accretion disks), due to the black hole rotating in the opposite direction as the galaxy. Further, that such accretion can be a factor in generating extreme emission from some galaxies, a reason why active galactic nuclei (AGNs) appear to fall into two classes: typical versus very bright. Such a situation is presumed to come about from galaxy mergers placing a SMBH in a galaxy rotating in the opposite direction.
Such accretion slows the SMBH's rotation, and sufficient such accretion reverses it. If the SMBH has doubled in mass over its lifetime, a past such reversal is a definite possibility. This is one possible mechanism for an observed reduction in the number of quasars over time: that mergers were common once, and sufficient time has passed to reverse the rotation of many of the SMBH's.