To engage in boisterous merrymaking; revel noisily.
To behave in a blustering manner; swagger.
[From obsolete roister, roisterer, probably from Old French rustre, ruffian, alteration of ruste, from Latin rūsticus, rustic; see rustic.] rois'ter·er n., rois'ter·ous adj., rois'ter·ous·ly adv.
1582, from an obsolete noun roister "noisy bully" (1551), from M.Fr. ruistre "ruffian," from O.Fr. ruste "rough country fellow," from L. rusticus (see rustic).