What is another word for most idiot-proof?
Pronunciation: [mˈə͡ʊst ˈɪdɪətpɹˈuːf] (IPA) 
When it comes to describing something that is completely foolproof, the possibilities for synonymous phrases are endless. Here are a handful of suggestions for words or phrases that could be used in place of "most idiot-proof." Some options include "idiot-resistant," "dummy-proof," "imbecile-proof," "fool-proof," "simple to use," and "easy as pie." Each of these phrases conveys the same message - that the designated item or process is nearly impossible to mess up, and won't cause any headaches for those who use it. No matter which phrase you choose to use, the sentiment remains the same - that this is something that anyone could succeed at.
