WordNet (r) 3.0 (2006):

stow away
    v 1: hide aboard a ship or a plane to get free transportation;
         "The illegal immigrants stowed away on board the freighter"

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "stow away":
   bank, bosom, bottle up, bundle away, bury, cache, coffer, deposit,
   embosom, file, file and forget, hide away, hutch, keep hidden,
   keep secret, lay away, lay down, lay in, lay in store, lock up,
   lodge, pack away, plant, put away, reposit, reservoir, salt away,
   salt down, seal up, secrete, stash, store, store away, stow,
   stow down, warehouse