ballast(redirected from class P ballast)
Also found in: Dictionary, Thesaurus, Financial, Encyclopedia, Wikipedia.
1. Material of doubtful value itself used to stabilize something (for example, maritime practice). 2. Something largely without intrinsic value.
Additional weight of material incorporated in a part of a contact lens to maintain it in a given orientation (Fig. B1). This is often provided by giving prismatic power to the lens (prism ballast lens).