洋洋 rarely stands alone. After a word for a feeling it means 'overflowing':
喜气洋洋 'full of festive joy',
得意洋洋 or
洋洋得意 'smug, pleased with oneself',
喜洋洋 'beaming'. Elsewhere it means 'vast, copious':
洋洋大观 'a grand and rich display',
洋洋洒洒 'running on at great length'.