English to English

noun (n)

• vertical space available to allow easy passage under something(noun.quantity)

  Synonym:
  clearance, headway
  

  source: wordnet30
• the capacity of a system to reproduce loud sounds without distortion(noun.act)

  Synonym:
  dynamic headroom
  

  source: wordnet30
• See Headway, 2.(noun)

  source: webster1913