A compound lens designed to correct both spherical and chromatic aberrations. ... (05 Mar 2000) ... 
one corrected for chromatic (color) and spheric aberration.
A lens that consists of three components. This enables lenses with short focal lengths to enjoy the same freedom from colour distortions as the longer focal length achromatic lenses
Type: Term Definitions: 1. a compound lens designed to correct both spherical and chromatic aberrations.