Three special classes of abstract
Witt rings are studied. The classical description of the annihilator of a round form is
generalized as is the description of the torsion subgroup of the Witt ring of a field.
We translate some results of a previous paper into this abstract setting and also
study Pfister forms there. We show how our special classes of abstract Witt rings
relate to the Witt ring of classes of nondegenerate symmetric bilinear forms over a
semilocal ring.