(n.) A companion in diversions; a playfellow.

ace amigo associate bedfellow bedmate birthmate bosom buddy buddy bunkie bunkmate butty camarade chamberfellow chum classmate clubmate colleague comate companion company compeer comrade concubine confrere consociate consort copartner copemate copesmate couchmate cradlemate crony cupmate doxy fellow fellow student friend general partner girl friend gossip jailmate kept mistress kept woman mate messmate mistress old crony pal paramour pard pardner partner pewmate playfellow roommate schoolfellow schoolmate secret partner shelfmate shipmate shopmate side partner sidekick sidekicker silent partner sleeping partner special partner tablemate teammate tentmate unofficial wife watchmate waymate woman workfellow yokefellow yokemate