Incorrect spelling, as the word is a mix of verb and suffix: explain (to define something, make it understandable) + -ation (which is here to form a noun) =, and then we must remember to omit i explanation is only correct form.

noun. the act or process of explaining. something that explains; a statement made to clarify something and make it understandable; exposition: an explanation of a poem. a meaning or interpretation: to find an explanation for a mystery.