WordWeb Online

1. Belonging to or on or near the back or upper surface of an animal or organ or part
   "the dorsal fin is the vertical fin on the back of a fish and certain marine mammals"
    
2. (biology) facing away from the axis of an organ or organism
   "the dorsal surface of a leaf is the underside or side facing away from the stem";
   - abaxial

Antonym: ventral

Encyclopedia: Dorsal