nounplural noun lustra/ˈlʌstrə/ , plural noun lustrums

• 1Roman History
  A purificatory sacrifice made after a census every five years.

  ‘The book is dedicated to Nygren's wife Irmgard "in thankfulness for seven lustrums of theological cooperation."’

  More example sentences

  • ‘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.’
• 2 rare A period of five years.