There are several synonyms for the phrase 'silent curses'. Some of them include muttering, whispering, mumbling, grumbling, babbling, humbling, sibilance, and suppressed anger. These words represent different ways in which a person can express their dissatisfaction or frustration without necessarily making a sound. Silent curses could be a result of someone feeling annoyed, angry, or upset about something, but they opt to keep quiet about it instead of speaking out. It is essential to note that silent curses can be harmful if they are not dealt with in the right way. It is crucial to find healthy ways to release negative emotions and communicate any issues to avoid internalizing them.