The Collaborative International Dictionary of English v.0.48:

Retch \Retch\ (r[e^]ch or r[=e]ch; 277), v. i. [imp. & p. p.
   Retched (r[e^]cht); p. pr. & vb. n. Retching.] [AS.
   hr[ae]can to clear the throat, hawk, fr. hraca throat; akin
   to G. rachen, and perhaps to E. rack neck.]
   To make an effort to vomit; to strain, as in vomiting.
   [Written also reach.]
   [1913 Webster]

         Beloved Julia, hear me still beseeching!
         (Here he grew inarticulate with retching.) --Byron.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Retch \Retch\, v. t. & i. [See Reck.]
   To care for; to heed; to reck. [Obs.] --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

retch
    n 1: an involuntary spasm of ineffectual vomiting; "a bad case
         of the heaves" [syn: heave, retch]
    v 1: eject the contents of the stomach through the mouth; "After
         drinking too much, the students vomited"; "He purged
         continuously"; "The patient regurgitated the food we gave
         him last night" [syn: vomit, vomit up, purge, cast,
         sick, cat, be sick, disgorge, regorge, retch,
         puke, barf, spew, spue, chuck, upchuck, honk,
         regurgitate, throw up] [ant: keep down]
    2: make an unsuccessful effort to vomit; strain to vomit [syn:
       gag, heave, retch]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "retch":
   barf, be nauseated, be seasick, be sick, bring up, choke on,
   chuck up, disgorge, egest, feed the fish, feel disgust, gag, heave,
   heave the gorge, keck, puke, regurgitate, reject, sick up,
   sicken at, spew, throw up, upchuck, vomit