The phrase "impose on or upon" refers to a situation where someone puts an obligation, burden or responsibility on someone else. There are several synonyms for this term, such as burden, obligate, encumber, weigh down, pressurize, or force upon. All of these words describe a situation where one person is attempts to cause another person to take on a task or responsibility, without giving them an option not to. These actions can range from subtly imposing a request to outright forcing someone to take on a task. Therefore, it is important to use these words carefully, as they can have significant impacts on how someone feels and behaves towards others.