sit in on

45 Moby Thesaurus words for "sit in on":
      attend, attend to, auscultate, be all ears, be enfranchised,
      be implicated in, bear a hand, bend an ear, bug, chip in,
      cock the ears, contribute, eavesdrop, enter into, examine by ear,
      give attention, give audience to, give ear, go into, hark,
      have suffrage, hear, hear out, hearken, heed, help decide,
      intercept, join, join in, lend an ear, listen, listen at,
      listen in, listen to, make the scene, partake, partake of,
      participate, participate in, pull an oar, sit in, take part in,
      tap, vote, wiretap