As a Noun:
1. An event in which something bad, such as an accident or disaster, very nearly happened. Idiomatic English = close shave, close call.
As a Verb or Adjective:
1. Of an accident or disaster, to very nearly happen. Idiomatic English = (be) a close shave, (be) a close call, (be) close, (be) very close.
1. Used alone to express your perception that an accident or disaster very nearly happened. English = 'That was close!', 'That was a close shave!', 'That was a close call!'