"Not perfect" is a phrase that implies an imperfection or flaw, which can be substituted with other synonyms such as "imperfect," "flawed," "defective," "blemished," or "incomplete." These synonyms can be used in a variety of contexts where the subject or object does not meet ideal or expected standards. For example, a piece of writing that has a few errors or mistakes can be described as flawed or imperfect, while a project or product that is not up to par or has some defects can be labeled as defective or blemished. These various synonyms provide a way to express a lack of perfection while still conveying the same meaning.