The Collaborative International Dictionary of English v.0.48:

corynebacterium \co`ry*ne`bac*ter"i*um\, n. (MIcrobiol.)
   Any member of the genus Corynebacterium, consisting of
   gram-positive usually nonmotile irregularly rod-shaped
   bacteria, some of which are pathogenic or parasitic in humans
   and domestic animals, such as Corynebacterium diphtheriae,
   which causes diphtheria.
   [PJC]

WordNet (r) 3.0 (2006):

Corynebacterium diphtheriae
    n 1: a species of bacterium that causes diphtheria [syn:
         Corynebacterium diphtheriae, C. diphtheriae, Klebs-
         Loeffler bacillus]