When something is deemed sub-par, it means it falls short of expectations or standards. Synonyms for more sub-par could include below-average, inferior, inadequate, unsatisfactory, or disappointing. Such words connote something that lacks the desired quality or capability. Other relevant terms could be insufficient, defective, flawed, mediocre, second-rate, or feeble. Using these synonyms can help to convey an impression of something that is not up to par, such as a sub-standard product or an underwhelming performance. It is important to select the correct word based on the intended meaning, as each term can have slightly different connotations.