wormwood

Short definition from Wiktionary

Noun

1. 1
   An intensely bitter herb (Artemisia absinthium and similar plants in genus Artemisia) used in medicine, in the production of absinthe and vermouth, and as a tonic.
2. 2
   Something that causes bitterness or affliction; a cause of mortification or vexation.

Proper noun

1. 1
   A star or angel that appears in the Book of Revelation, turning waters bitter and poisonous.
2. 2
   A surname.