The Collaborative International Dictionary of English v.0.48:

germicidal \ger"mi*ci`dal\ (j[~e]r"m[i^]*s[imac]`dal), a. [Germ
   + L. caedere to kill + -al.] (Biol.)
   Destructive to germs; -- applied to any agent which has a
   killing action upon living microorganisms, particularly
   bacteria or viruses, which are the cause of many infectious
   diseases.

   Syn: antiseptic.
        [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

germicidal
    adj 1: preventing infection by inhibiting the growth or action
           of microorganisms [syn: bactericidal, disinfectant,
           germicidal]