"Be seemly" is an idiomatic phrase that means to behave or dress in a manner that is appropriate and suitable for a particular situation. The antonyms of "be seemly" are words that convey the opposite meaning, such as inappropriate, unsuitable, unbecoming, indecent, and unacceptable. If one's behavior or clothing is described as inappropriate or unsuitable, it implies that they have breached social norms or standards of decency. Unbecoming carries the connotation of something that is unattractive, improper, or not fitting for the person or the context. Similarly, unacceptable means that something is not approved or allowed due to its offensive or inappropriate nature, and indecent suggests something that is offensive to public morality.