Praxis and solipsism are two of the words whose definitions I forget the moment after I look them up. I only really encounter the former in academic writing, and the latter in philosophy texts/Meredith’s vocabulary. (Not always mutually exclusive.) So here are their definitions, according to Merriam Webster:
Praxis: action or practice: as an exercise or practice of an art, science, or skill/customary practice or conduct.
Solipsism: a theory holding that the self can know nothing but its own modifications and that the self is the only existent thing.
Thanks, internet dictionaries!