WordNet (r) 3.0 (2006):

all together
    adv 1: all at the same time; "Let's say `Yes!' all at once"
           [syn: all together, all at once]
    2: used of a group whose members acted or were acted upon
       collectively and when `all' and `together' can be separated
       by other words; "they were herded all together"; "they were
       all herded together"; "the books lay all together in a heap";
       "the books all lay together..."

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "all together":
   all agreeing, all at once, as one, as one man, at a blow,
   at a clip, at a stroke, at once, at one blow, at one jump,
   at one stroke, at one swoop, at one time, by acclamation,
   coinstantaneously, concurrently, conjointly, consentaneously,
   corporately, forthwith, in a chorus, in a hurry, in agreement,
   in chorus, in common, in concert with, in concord, in partnership,
   in phase, in sync, in unison, inharmony, isochronously, jointly,
   mutually, nem con, nemine contradicente, nemine dissentiente, now,
   on all hands, on the beat, one and all, per saltum, pronto,
   right away, right now, right off, simultaneously, straightaway,
   straightway, subito, synchronously, then and there, this minute,
   this very minute, to a man, together, unanimously, uno saltu,
   with one accord, with one consent, with one voice,
   without contradiction, without delay