1. in a way that shows strong feelings of anger, hurt, or resentment
2. extremely or intensely (used to emphasize unpleasant conditions)
3. with a sharp, unpleasant taste

Examples

• She complained bitterly about the unfair treatment.
• The two former friends argued bitterly over money.
• It was bitterly cold outside during the snowstorm.
• He bitterly regretted his decision to quit school.
• The medicine tasted bitterly unpleasant.
• They were bitterly disappointed by the election results.
• The wind blew bitterly across the frozen lake.