As a Noun: 1. The act of taking in air into your lungs and letting it out again. English = breathing. Formal medical English = respiration. 2. The two parts of your body inside your chest which fill with air when you breathe. English = lungs. As a Verb or Adjective: 1. To take in air into your lungs and let it out again. English = breathe. 2. Of, relating to, or affecting breathing (respiration) or the organs of respiration (the lungs). English = respiratory.