WordNet (r) 3.0 (2006):

work in
    v 1: add by mixing or blending on or attaching; "work in the
         butter and the dough will get the right consistency"; "In
         his speech, the presidential candidate worked in a lot of
         learned words"

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "work in":
   admit, barge in, be admitted, break in, break in upon, breeze in,
   burst in, bust in, butt in, charge in, come barging in,
   come between, come breezing in, come busting in, come in, crash,
   crash in, crash the gates, creep in, cross the threshold, crowd in,
   cut in, drag in, drop in, edge in, elbow in, encroach, enter,
   entrench, foist, foist in, fudge in, gain admittance, get in,
   go in, go into, have an entree, have an in, hop in, horn in,
   impinge, implant in, impose, impose on, impose upon, infiltrate,
   infringe, inject in, insert, insert in, insinuate, insinuate in,
   intercalate, interfere, interjaculate, interject, interlope,
   interpolate, interpose, intervene, introduce in, intrude, invade,
   irrupt, jam in, jump in, look in, lug in, obtrude, pack in, pop in,
   press in, push in, put between, put in, put on, put upon, run in,
   rush in, sandwich, set foot in, slink in, slip in, smash in,
   smuggle in, sneak in, squeeze in, steal in, step in, storm in,
   take in, throng in, throw in, thrust in, trench, trespass, visit,
   wedge in, worm, worm in