The Collaborative International Dictionary of English v.0.48:

Enclitic \En*clit"ic\, n. (Gram.)
   A word which is joined to another so closely as to lose its
   proper accent, as the pronoun thee in prithee (pray thee).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Enclitic \En*clit"ic\ ([e^]n*kl[i^]t"[i^]k), Enclitical
\En*clit"ic*al\ ([e^]n*kl[i^]t"[i^]*kal), a. [L. encliticus, Gr.
   'egkli`tikos, fr. 'egkli`nein to incline; 'en in + kli`nein
   to bend. See In, and Lean, v. i.] (Gram.)
   Affixed; subjoined; -- said of a word or particle which leans
   back upon the preceding word so as to become a part of it,
   and to lose its own independent accent, generally varying
   also the accent of the preceding word.
   [1913 Webster]