Meaning of cornet-à-pistons

cor•net-à-pis•tons

Pronunciation: (kôr-net'u-pis'tunz Fr. kôr-ne-a-pē-stôn'), [key]
— pl. cor•nets-à-pis•tons
  1. cornet (def. 1).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.