noun

• (Egyptian mythology) The Egyptian god of the Sun.
• (geology) Any of a series of moraines, in parts of Norway, that are long ridges covered with stones.
• Alternative form of RA (republican army; IRA).
• (medicine) Initialism of rheumatoid arthritis. [(pathology) A chronic and progressive disease in which the immune system attacks the joints. It is characterised by pain, inflammation and swelling of the joints, stiffness, weakness, loss of mobility and deformity. Tissues throughout the body can be affected, including the skin, blood vessels, heart, lungs, and muscles.]
• (anatomy, medicine) Initialism of right atrium. [(anatomy) The chamber of the heart, in humans and other mammals, that receives deoxygenated blood from the venae cavae and pumps it into the right ventricle.]
• (military) Initialism of rear admiral, a rank in the Royal Navy. [(military, nautical) A naval officer below the rank of vice admiral, originally in charge of a fleet's rear formation.]
• Initialism of Royal Academician, a member of the Royal Academy.
• Initialism of resident assistant, a trained student leader, within a college or university, who is given the responsibility of supervising students living in a residence hall.
• Initialism of Restricted Area, an area that only authorized people can enter. See also Exclusion zone.
• (aviation) Initialism of resolution advisory (a type of TCAS warning). [(aviation) A TCAS warning directing the pilot of an aircraft to take immediate evasive action of a specified type (for instance: "INCREASE CLIMB, INCREASE CLIMB") to avoid a possible impending mid-air collision.]
• Initialism of rescue ambulance.
• Initialism of research assistant [An individual who assists a researcher, often on a contractual basis, with research in a commercial, academic, or private setting.]
• Initialism of Royal Academy, the Royal Academy of Arts is an art institution based in London, England.
• Initialism of Royal Artillery, a regiment in the British Army.
• Initialism of Republic of Armenia. [The official name of Armenia.]
• Initialism of republican army, most often the Provisional IRA.