lustrum
/ˈlʌstrəm
/noun (plural lustra /ˈlʌstrə/ or lustrums) chiefly literary or historical
A period of five years.The book is dedicated to Nygren's wife Irmgard "in thankfulness for seven lustrums of theological cooperation."...
- 37 years ago my first secretary was a lady who has remained my friend for nearly 8 lustrums (4 decades) and today is a leading lady lawyer in Los Angeles who has never lost a case in court.
Origin
Late 16th century: from Latin, originally denoting a purificatory sacrifice after a quinquennial census.