The term 'state of perfect happiness' can be defined by four crossword solutions: NIRVANA (7 letters), ELYSIUM (7 letters), UTOPIA (6 letters) and PARADISE (8 letters). NIRVANA is a Buddhist concept of enlightenment, which is a state of perfect peace and joy. ELYSIUM is a place in Greek mythology where the souls of the heroic and virtuous go after death. UTOPIA is an ideal society, as described in Thomas More's book of the same name. Finally, PARADISE is a place of perfect bliss and delight, as described in the Bible.