There are various synonyms for the word "mind-boggler" which is used to describe a situation, concept, or idea that's difficult to understand or comprehend. Some of the synonyms include perplexing, confounding, puzzling, mystifying, enigmatic, and baffling. These words are often used to describe something that can leave a person feeling confused or struggling to make sense of it. Additionally, they connote a sense of mystery and intrigue, leaving individuals curious to gain a deeper understanding. As such, whether it's a complex concept, puzzle, or riddle, using one of these synonyms for "mind-boggler" can help you communicate the idea more effectively.