As a Noun: 1. Something such as a rule, law, or policy that makes it difficult or impossible for something to happen or be achieved; or a problem that prevents two people or groups from agreeing, communicating, or working with each other. English = barrier, obstacle. 2. As a Verb or Adjective: 1. Of telecommunications (phones, TTYs, etc.), to be already in use, so you cannot communicate with the person you are trying to contact. English = (be) busy, (be) engaged. 2. Idiomatic English = unable to get through, unable to be put through.