Septemˈbrist noun

1. A participator in the September massacres of royalist prisoners in Paris, 2–7 September 1792 (Fr hist)
2. A supporter of the successful rising of 1836 in Portugal

Sepˈtembrizer or Sepˈtembriser noun

1. A Septembrist (French and Portuguese historical)
2. A partridge-shooter, esp one active in September

September people plural noun (informal; euphemistic)

People of late middle age or older