Keywords: obstacle, barrier, busy, engaged (busy)

Sign Definition

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.

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.