From Longman Dictionary of Contemporary EnglishI shudder to thinkI shudder to thinkspokenBAD used to say that you do not want to think about something because it is too unpleasant I shudder to think what they’ll say when they see the mess the house is in. → shudder
Examples from the Corpus
I shudder to think• I never know how carefully. I shudder to think.• Palestrina! I shudder to think what I should do when her next social invitation arrives in the letter box!• I regularly see them sent out alone on shopping errands. I shudder to think what might happen on their way home.• I shudder to think what will happen to him now. 