The Collaborative International Dictionary of English v.0.48:

Liriodendron \Lir`i*o*den"dron\
   (l[i^]r`[i^]*[-o]*d[e^]n"dr[o^]n), n.; pl. Liriodendra
   (-dr[.a]). [NL., fr. Gr. lei`rion lily + de`ndron tree.]
   (Bot.)
   A genus of large and very beautiful trees of North America,
   having smooth, shining leaves, and handsome, tuliplike
   flowers; tulip tree; whitewood; -- called also canoewood.
   Liriodendron tulipifera is the only extant species, but
   there were several others in the Cretaceous epoch.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Liriodendron
    n 1: tulip trees [syn: Liriodendron, genus Liriodendron]