The antonyms for the word "busts open" can vary depending on the context in which the phrase is being used. However, some possible opposite meanings could include phrases such as "closes tightly," "seals shut," "locks securely," "stays intact," or "remains unbroken." These opposite phrases suggest a lack of force or an absence of action, rather than the explosive, forceful imagery of "busts open." They convey a sense of containment, security, and stability, rather than the sudden release or exposure implied by the original phrase.