WordNet (r) 3.0 (2006):

lemon balm
    n 1: bushy perennial Old World mint having small white or
         yellowish flowers and fragrant lemon-flavored leaves; a
         garden escapee in northern Europe and North America [syn:
         lemon balm, garden balm, sweet balm, bee balm,
         beebalm, Melissa officinalis]
    2: lemony leaves used for a tisane or in soups or fruit punches