WordNet sense 1 (an unofficial association of people or groups):

band, lot, set

WordNet sense 2 (a road junction at which traffic streams circularly around a central island):

rotary, roundabout, traffic circle

WordNet sense 3 (street names for flunitrazepan):

roach, rope, roofy, rophy, forget me drug, Mexican valium

WordNet sense 4 (a curved section or tier of seats in a hall or theater or opera house; usually the first tier above the orchestra):

dress circle

WordNet sense 5 (any circular or rotating mechanism):

round

WordNet sense 6 (be around):

encircle, ring, surround, environ

WordNet sense 7 (move in circles):

circulate

WordNet sense 8 (movement once around a course):

circuit, lap