[1] : WordNet (r) 2.0

throw in
     v 1: add as an extra or as a gratuity
     2: give up in the face of defeat of lacking hope; admit defeat;
        "in the second round, the challenger gave up" syn: drop
        out, give up, fall by the wayside, drop by the
        wayside, throw in the towel, quit, chuck up the
        sponge ant: enter
     3: to insert between other elements; "she interjected clever
        remarks" syn: interject, come in, interpose, put
        in, inject
see also:
drop out give up fall by the wayside drop by the wayside throw in the towel quit 
chuck up the sponge enter interject come in interpose 
put in inject 

[2] : Moby Thesaurus II by Grady Ward, 1.0

44 moby thesaurus words for "throw in":
   contribute, drag in, ease in, edge in, fill in, foist in, fudge in,
   implant in, infuse, inject, inject in, inoculate, insert,
   insert in, insinuate, insinuate in, intercalate, interjaculate,
   interject, interpolate, interpose, intervene, introduce,
   introduce in, intromit, intrude, lug in, perfuse, pop in,
   put between, put in, run in, sandwich, set in, slip in, smuggle in,
   squeeze in, stick in, thrust in, tuck in, wedge in, whip in,
   work in, worm in

Throw >> T Words
Throw, definition of term: Throw
throw_pag1.html

Throw Out >> T Words
Throw Out, definition of term: Throw Out
throw+out_pag1.html

Throw Up >> T Words
Throw Up, definition of term: Throw Up
throw+up_pag1.html

Throw In >> T Words
Throw In, definition of term: Throw In
throw+in_pag1.html

Throw Away >> T Words
Throw Away, definition of term: Throw Away
throw+away_pag1.html

Stones Throw >> S Words
Stones Throw, definition of term: Stones Throw
stones+throw_pag1.html

Free Throw >> F Words
Free Throw, definition of term: Free Throw
free+throw_pag1.html