The Collaborative International Dictionary of English v.0.48:
Eucalyptus \Eu`ca*lyp"tus\, n. [NL., from Gr. e'y^ well, good +
? covered. The buds of Eucalyptus have a hemispherical or
conical covering, which falls off at anthesis.] (Bot.)
A myrtaceous genus of trees, mostly Australian. Many of them
grow to an immense height, one or two species exceeding the
height even of the California Sequoia.
Syn: eucalyptus tree, gum tree, eucalypt. [1913 Webster]
Note: They have rigid, entire leaves with one edge turned
toward the zenith. Most of them secrete resinous gums,
whence they called gum trees, and their timber is of
great value. Eucalyptus Globulus is the blue gum; E.
gigantea, the stringy bark: E. amygdalina, the
peppermint tree. E. Gunnii, the Tasmanian cider tree,
yields a refreshing drink from wounds made in the bark
in the spring. Other species yield oils, tars, acids,
dyes and tans. It is said that miasmatic valleys in
Algeria and Portugal, and a part of the unhealthy Roman
Campagna, have been made more salubrious by planting
groves of these trees.