WordNet (r) 3.0 (2006):

en masse
    adv 1: all together; "the students turned out en masse" [syn:
           en masse, en bloc, as a group]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "en masse":
   across the board, all, all at once, all in all, all put together,
   altogether, as a body, as a whole, at large, bodily, collectively,
   communally, conjointly, corporately, en bloc, ensemble, entirely,
   in a body, in all, in all respects, in association, in bulk,
   in company, in conjunction, in its entirety, in the aggregate,
   in the gross, in the lump, in the mass, in toto, jointly, mutually,
   on all counts, on the whole, together, totally, tout ensemble,
   unitedly, wholly