A festering, embittering object or condition, either mental, or a physical sore or ulcer.
To fester.
To cause irritation or deep bitterness.
Something that causes bitterness or affliction; a cause of mortification or vexation.
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.