If you do something imperfectly, you do it, but not all the way right — not fully, not smoothly, not without gaps. We remember things imperfectly. The idea was imperfectly explained. It is a fair, slightly formal adverb. It does not always mean badly. Sometimes it only means in part, or not yet complete: a plan imperfectly thought out still exists; it just has holes. Though actually, grammar books also use imperfect for a kind of past tense in other languages. This adverb is almost never about that school meaning. It is about not being perfect, in the ordinary human way.