The phrase "imposing an onus" means to place a burden, responsibility, or obligation on someone. There are various synonyms for this phrase, including foisting, saddling, imposing, thrusting, burdening, pressuring, enforcing, obligating, assigning, and requiring. All of these words share the common theme of placing a duty or obligation on an individual or group. The use of synonyms can enhance the clarity and variety of communication, allowing for more precise and nuanced language. When seeking to communicate a sense of responsibility or obligation, using synonyms for "imposing an onus" can help to emphasize the gravity and importance of the situation.