To breathe quickly and deeply, especially at an abnormally rapid rate.
To draw air into the lungs, through the nose or mouth by action of the diaphragm.
To draw air or any form of gas (either in a pure form, or mixed with small particles in form of aerosols/smoke -sometimes stemming from a medicament) into the lungs, through the nose or mouth by action of the diaphragm.
To eat very quickly.
An inhalation.