The Collaborative International Dictionary of English v.0.48:

Poplar \Pop"lar\, n. [OE. popler, OF. poplier, F. peuplier, fr.
   L. populus poplar.] (Bot.)
   1. Any tree of the genus Populus; also, the timber, which
      is soft, and capable of many uses.
      [1913 Webster]

   Note: The aspen poplar is Populus tremula and Populus
         tremuloides; Balsam poplar is Populus balsamifera;
         Lombardy poplar (Populus dilatata) is a tall, spiry
         tree; white poplar is Populus alba.
         [1913 Webster]

   2. The timber of the tulip tree; -- called also white
      poplar. [U.S.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tacamahac \Tac"a*ma*hac`\, Tacamahaca \Tac`a*ma*ha"ca\, n.
   1. A bitter balsamic resin obtained from tropical American
      trees of the genus Elaphrium (Elaphrium tomentosum and
      Elaphrium Tacamahaca), and also from East Indian trees
      of the genus Calophyllum; also, the resinous exhudation
      of the balsam poplar.
      [1913 Webster]

   2. (Bot.) Any tree yielding tacamahac resin, especially, in
      North America, the balsam poplar, or balm of Gilead
      (Populus balsamifera).
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Balm \Balm\ (b[aum]m), n. [OE. baume, OF. bausme, basme, F.
   baume, L. balsamum balsam, from Gr. ba`lsamon; perhaps of
   Semitic origin; cf. Heb. b[=a]s[=a]m. Cf. Balsam.]
   [1913 Webster]
   1. (Bot.) An aromatic plant of the genus Melissa.
      [1913 Webster]

   2. The resinous and aromatic exudation of certain trees or
      shrubs. --Dryden.
      [1913 Webster]

   3. Any fragrant ointment. --Shak.
      [1913 Webster]

   4. Anything that heals or that mitigates pain. "Balm for each
      ill." --Mrs. Hemans.
      [1913 Webster]

   Balm cricket (Zool.), the European cicada. --Tennyson.

   Balm of Gilead (Bot.), a small evergreen African and
      Asiatic tree of the terebinthine family (Balsamodendron
      Gileadense). Its leaves yield, when bruised, a strong
      aromatic scent; and from this tree is obtained the balm of
      Gilead of the shops, or balsam of Mecca. This has a
      yellowish or greenish color, a warm, bitterish, aromatic
      taste, and a fragrant smell. It is valued as an unguent
      and cosmetic by the Turks. The fragrant herb
      Dracocephalum Canariense is familiarly called balm of
      Gilead, and so are the American trees, Populus
      balsamifera, variety candicans (balsam poplar), and
      Abies balsamea (balsam fir).
      [1913 Webster]

WordNet (r) 3.0 (2006):

Populus balsamifera
    n 1: poplar of northeastern North America with broad heart-
         shaped leaves [syn: balsam poplar, hackmatack,
         tacamahac, Populus balsamifera]