WordNet (r) 3.0 (2006):

lime tree
    n 1: any of various related trees bearing limes [syn: lime,
         lime tree, Citrus aurantifolia]
    2: any of various deciduous trees of the genus Tilia with heart-
       shaped leaves and drooping cymose clusters of yellowish often
       fragrant flowers; several yield valuable timber [syn:
       linden, linden tree, basswood, lime, lime tree]