D defs.my
Entry 1 sense Webster, 1913

Cachet

/kăsh'-ā/ · Cach·et · IPA /kæˈʃeɪ/
01 n. A seal, as of a letter.
  1. 1.
    A seal, as of a letter.
Phrases & compounds
Lettre de cachet — a sealed letter, especially a letter or missive emanating from the sovereign; -- much used in France before the Revolution as an arbitrary order of imprisonment.