sub rosa

/ˈsʌb ˌroʊzə/

Use the Latin phrase sub rosa to describe something that's done in secret. Your espionage club might hold all its meetings sub rosa, in your tree house in the middle of the night.

Spies operate sub rosa, and you might save all the ice cream to eat it sub rosa in the kitchen after your family's asleep. In Latin, the phrase means "under the rose" and refers to the tradition, going back to ancient Greece and Rome, of using a rose to symbolize secrecy. Roman banquet rooms sometimes had roses painted on the walls to remind wine-drinkers that anything said sub vino ("under the influence of wine") should also stay sub rosa.

Definitions of sub rosa

1. adverb

   in secret or covertly
   “held a meeting sub rosa to avoid general criticism”