from
The Collaborative International Dictionary of English v.0.48
Tusk \Tusk\, n. [OE. tusk, the same word as tusch, AS. tusc. See
{Tush} a tooth.]
1. (Zool.) One of the elongated incisor or canine teeth of
the wild boar, elephant, etc.; hence, any long, protruding
tooth.
[1913 Webster]
2. (Zool.) A toothshell, or Dentalium; -- called also
{tusk-shell}.
[1913 Webster]
3. (Carp.) A projecting member like a tenon, and serving the
same or a similar purpose, but composed of several steps,
or offsets. Thus, in the illustration, a is the tusk, and
each of the several parts, or offsets, is called a tooth.
[1913 Webster]