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]