re·group / rēˈgroōp/ • v. [intr.] (of troops) reassemble into organized groups, typically after being attacked or defeated: their heroic resistance gave American forces time to regroup. ∎ [tr.] cause to reassemble in this way: he regrouped his fighters in the hills. ∎ [tr.] rearrange (something) into a new group or groups: she was regrouping the numeric data.DERIVATIVES: re·group·ment n.