Buna is a census-designated place in Jasper County, Texas, United States. The population was 2,142 at the 2010 census.
Gas Exchange. Gas exchange is the process by which oxygen and carbon dioxide (the respiratory gases) move in opposite directions across an organism's respiratory membranes, between the air or water of the external environment and the body fluids of the internal environment.
Princeton's WordNet(3.67 / 3 votes)Rate this definition: exchange(noun) chemical process in which one atom or ion or group changes places with another. exchange(noun) a mutual expression of views (especially an unpleasant one) they had a bitter exchange. exchange, interchange(noun) the act of changing one thing for another thing.