The Collaborative International Dictionary of English v.0.48:

Tmesis \Tme"sis\ (m[=e]"s[i^]s or t'm[=e]"s[i^]s; 277), n. [L.,
   from Gr. tmh^sis a cutting, fr. te`mnein to cut.] (Gram.)
   The separation of the parts of a compound word by the
   intervention of one or more words; as, in what place soever,
   for whatsoever place.
   [1913 Webster]