1. A stopping of the pulse because of pathological (disease or illness) changes that are caused by a lack of oxygen when breathing air, resulting in hypoxia and hypercapnia: Asphyxia is a condition in which there is an extreme decrease in the concentration of oxygen in the body that is accompanied by an increase in the concentration of carbon dioxide which can result in a loss of consciousness or even death.

Asphyxia can result from choking, drowning, electric shock, injury, or the breathing in of non-toxic or toxic gases.

2. Etymology: from Latin asphyxia, borrowed from Greek asphyxia, "a stopping of the pulse"; from a-, "without" + sphyxis, "pulse"; from sphyzein, "to throb", of uncertain origin.