impassable / impassible are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
impassable: (adjective) incapable of being passed.
impassible: NA
impassable: ih·m·p·AE·s·ah·b·ah·l
impassible: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)