There are multiple synonyms for the phrase "laugh grimly about." Some of the most common ones include "chuckle bitterly," "smirk wryly," and "snicker mockingly." These phrases often convey a sense of dark humor or sarcastic amusement. Other synonyms may include "giggle cynically," "grin sardonically," or "smile derisively." Each of these phrases implies a specific emotion or attitude, and can be used to describe different types of situations where someone may be laughing in a not so pleasant way. Whether it's a dark joke or a mocking remark, these synonyms can help you better express your thoughts and feelings.