1. To bar someone or something from entry into some place. The first noun or pronoun can also come after "off." Police sealed the building off from the public while the investigation took place. We need to find a way to seal off the store room from these rodents.

2. To completely isolate someone or something from someone or something else; to make someone or something totally inaccessible to someone or something else. The first noun or pronoun can also come after "off." The prison warden sealed off the inmate from the rest of the prisoners. The museum sealed the artifact off from visitors after the attempted theft.