the blood group whose red cells carry the A antigen
Atmospheres containing acetylene.
In relation to motorsport governed by the FIA, Group A referred to a set of regulations providing production-derived vehicles for outright competition. In contrast to the short-lived Group B and the Group C, the Group A referred to production-derived vehicles limited in terms of power, weight, allowed technology and overall cost. Group A was aimed at ensuring a large number of privately-owned entries in races.