The Collaborative International Dictionary of English v.0.48:

Hyssop \Hys"sop\, n. [OE. hysope, ysope, OF. ysope, F. hysope,
   hyssope, L. hysopum, hyssopum, hyssopus, Gr. ?, ?, an
   aromatic plant, fr. Heb. [=e]sov.]
   A plant (Hyssopus officinalis). The leaves have an aromatic
   smell, and a warm, pungent taste.
   [1913 Webster]

   Note: The hyssop of Scripture is supposed to be a species of
         caper (Capparis spinosa), but probably the name was
         used for several different plants.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Hyssopus officinalis
    n 1: a European mint with aromatic and pungent leaves used in
         perfumery and as a seasoning in cookery; often cultivated
         as a remedy for bruises; yields hyssop oil [syn: hyssop,
         Hyssopus officinalis]