Mark's definition (Unusual regularity in the form of a flower that is normally irregular.) could be a bit confusing. A peloric flower is one in which a flower that is normally zygomorphic, or bilaterally symmetrical, develops as an actinomorphic flower, or one that is radially symmetrical. In other words, a flower that is symmetrical when divided on ONE plane, becomes one that is divisible on many.
Furthermore, I would suggest that a flower that is bilaterally symmetric is very regular (it is, afterall, a mirror image).