How is electron richness defined?

What does it mean for an atom/molecule to be electron rich? For instance, why is the methyl carbanion considered electron rich (having excess electrons) even though it has a complete octet, no more, no less? I know that if the octet is incomplete, an atom/molecule is considered electron deficient, but how exactly is electron richness defined? I was under the impression that electron richness referred to atoms/molecules which had more than 8 electrons on the central atom.


