The phrase "fills the bill" typically means that something is satisfactory or fits the description of what is needed or wanted. Antonyms for this phrase might include "falls short," "doesn't measure up," or "misses the mark." These words indicate that the item or situation in question does not meet the necessary criteria or expectations. Other antonyms might include "unsuitable," "inadequate," or "insufficient." These terms all imply that the item or situation is not appropriate or sufficient for the intended purpose. When looking for the opposite of "fills the bill," it is important to consider words that convey a sense of deficiency or inadequacy.