(noun, usu. female) nymphomaniac of the submissive variety, extremely devoted and generally long-sufferingly obedient to male members.
Derived from but not to be confused with cocker spaniel. Heavy and/or sagging breasts are not part of the definition.
Would you look at Denise? The longing look in her eyes when she sees a bulge in anyone's pants. She's such a cock spaniel!