noun

• (transport, international law) The Agreement on the International Carriage of Perishable Foodstuffs and on the Special Equipment to be used for such Carriage (ATP).
• (tennis) Initialism of Association of Tennis Professionals: the governing body of men's professional tennis, formed in 1972.
• (biochemistry) Initialism of adenosine triphosphate. [(biochemistry) a nucleotide that is used as a source of energy in cellular reactions, in the synthesis of nucleic acids, and as a neurotransmitter recognised by purinergic receptors]
• (law, project management) Initialism of authorization to proceed.
• (finance) Initialism of average transaction price.
• (rail transport) Initialism of automatic train protection.
• (aviation) Initialism of airline transport pilot.