Roister is an old English verb meaning to engage in boisterous or rowdy behavior. It can be broken down into the crossword solutions ROMP (4 letters), CELEBRATE (9 letters), CAROUSE (7 letters), GAMBOL (6 letters), BLUSTER (7 letters), and REVEL (5 letters). ROMP means to play or frolic in a lively manner, CELEBRATE means to mark an occasion with festivities, CAROUSE means to engage in boisterous drinking and merrymaking, GAMBOL means to skip or leap about playfully, BLUSTER means to make a great show of strength or courage, and REVEL means to take part in lively and noisy festivities. All of these activities are associated with roistering.