The term 'in perpetuity' means something that will last forever. The crossword solutions for this term are EVER (4 letters), EVERMORE (8 letters), FORLII (6 letters), and FORERANDER (10 letters). EVER is an adverb meaning at all times, while EVERMORE is an adverb meaning forever. FORLII is an archaic word meaning forever, and FORERANDER is an archaic word meaning forevermore. All of these words indicate something that will last forever.