bitter herb

noun

1. an Old World herb, Centaurium erythraea, used dried in medicine as a tonic.
2. the turtlehead, Chelone glabra, used in medicine as a tonic, cathartic, and anthelmintic.
3. Judaism. an herb that tastes bitter, as horseradish, traditionally eaten at the Seder, and serving as a reminder of the Israelites’ slavery in Egypt.