The Collaborative International Dictionary of English v.0.48:

Labdanum \Lab"da*num\, n. (Bot.)
   See Ladanum.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ladanum \Lad"a*num\, n. [L. ladanum, ledanum, Gr. la`danon,
   lh`danon, fr. lh^don name of a shrub, mastic; cf. Per.
   l[=a]dan, l[=a]den. Cf. Laudanum.]
   A gum resin gathered from certain Oriental species of
   Cistus. It has a pungent odor and is chiefly used in making
   plasters, and for fumigation. [Written also labdanum.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

labdanum
    n 1: a dark brown to greenish oleoresin that has a fragrant odor
         and is used as a fixative in perfumes; obtained as a juice
         from certain rockroses [syn: labdanum, gum labdanum]
    2: a soft blackish-brown resinous exudate from various rockroses
       used in perfumes especially as a fixative [syn: labdanum,
       ladanum]