The antonyms for the phrase "be marked at" are "be unmarked," "be blank," or "be unidentified." When something is marked, it means that it has a notation or symbol, indicating its significance or value. However, when something is unmarked, it is without any noticeable characteristic, and can be easily overlooked. A blank item has no information or indication of its purpose. Unidentified objects have not been assigned a specific name or classification. It is essential to understand antonyms to build a broader and more nuanced vocabulary. This helps in better communication and comprehension, and is vital in both academic and professional settings.