COMMON You say the mind boggles when you find something difficult to imagine or understand because it is so surprising, strange, or complicated. With technology like this, the mind boggles at what geography classes will be like in the not-too-distant future. The mind boggles to think what they could eventually achieve. Note: You can also say that something boggles the mind or that it boggles your mind with the same meaning. Such statements boggle the mind. Talk about amazing coincidences — this one absolutely boggled my mind. Note: You can also describe something very surprising, strange, or complicated as mind-boggling. The mind-boggling 2,100-page timetable comes complete with a 40-page supplement. The range of products on offer is simply mind-boggling. Note: The word `boggle' is probably derived from the word `bogle', which is an old-fashioned word for an evil spirit or `bogey', as in `bogey man'.