The first has to do with how well expectations line up with actualities, whether they are realised or thwarted in the course of one's life. From Cambridge English . Thwart definition is - to oppose successfully: defeat the hopes or aspirations of. How to use thwart in a sentence. Did You Know? Synonym Discussion of thwart. Thwart definition, to oppose successfully; prevent from accomplishing a purpose. Sadly for the NRA, we are in the Information Age, and the truth is starting to.