Merriam-Webster Collegiate Dictionary - impassible

 I. adjective  Etymology: Middle English, from Middle French or Late Latin; Middle French, from Late Latin impassibilis, from Latin in- + Late Latin passibilis passible  Date: 14th century  1.  a. incapable of suffering or of experiencing pain  b. inaccessible to injury  2. incapable of feeling ; impassive  • impassibility noun  • impassibly adverb  II. variant of impassable