- The definition of implausible is something that is unlikely to be true.
A plot point in a story that makes no sense and that readers universally agree would not be something the characters do is an example of something that would be described as implausible.
implausible definition by Webster's New World
implausible definition by American Heritage Dictionary
- im·plauˌsi·bilˈi·ty noun
- im·plauˈsi·bly adverb