The Collaborative International Dictionary of English v.0.48:

Dictamnus \Dic*tam"nus\ (d[i^]k*t[a^]m"n[u^]s), n. [L. See
   Dittany.] (Bot.)
   A suffrutescent herb, Dictamnus Fraxinella (the only
   species), with strong perfume and showy flowers. The volatile
   oil of the leaves is highly inflammable.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Dictamnus
    n 1: a dicotyledonous genus of the family Rutaceae [syn:
         Dictamnus, genus Dictamnus]