There are several antonyms for the phrase "doth to a t," which means to do something perfectly or precisely. One possible antonym is "careless," meaning to do something without attention or concern for accuracy. Another antonym could be "imperfect," which denotes an action that is not done flawlessly. "Roughly" is also an antonym for doing something to a t, signifying a lack of refinement or polish. Additionally, "faulter" could serve as an antonym, representing someone who is inconsistent or unsteady in their execution. Overall, each of these antonyms provides a clear contrast to the idea of doing something to a t, emphasizing a lack of attention to detail or a failure to accomplish a task flawlessly.