Seethe/siːð/ Definition 1 of 3Pro Tip 1/3Silent Fury Use 'seethe' to describe extreme internal anger without obvious outward signs. Despite her calm appearance, she was seething inside. Pro Tip 2/3Sustained Anger 'Seethe' implies a lasting anger, not just a fleeting irritation. He continued to seethe long after the argument was over. Pro Tip 3/3Intensity Matters The word 'seethe' is used for very strong emotions, not for minor annoyances. She was seething with animosity after the betrayal.