The phrase "in one ear" is often used to describe something that has been heard but not fully absorbed or understood. There are several synonyms that can be used to convey a similar meaning, such as "one ear and out the other," "in passing," "overheard," "ignored," and "dismissed." These words emphasize the idea of hearing something but not giving it enough attention or consideration. Other related phrases include "tuned out," "not registering," and "disregarded." It is important to remember that while these words may be interchangeable in certain contexts, they may have slightly different implications and connotations depending on the situation.