The Collaborative International Dictionary of English v.0.48:

regroup \regroup\, re-group \re-group\v. i. & t.
   To reorganize into new groups; to reform a group that has
   been dispersed. The spelling without the hyphen is more
   common.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

regroup
    v 1: organize anew, as after a setback [syn: reorganize,
         reorganise, regroup]
    2: reorganize into new groups