Misapprehend is a verb that means to misunderstand. One place you definitely don't want to misapprehend instructions is on the plane when you're getting ready to skydive for the first time!
The word misapprehend is sometimes used as a synonym for the word misunderstand, so you can use it in a similar way, but more for misunderstanding meaning than mishearing. Since apprehend means to grasp or catch, misapprehend can likewise mean to not grasp knowledge or information. For example, if someone is speaking in scientific lingo about acrocentric chromosomes and locus heterogeneity, and you don't understand what they're talking about, you might ask them to clarify in different terms so you don't misapprehend what they're saying.