Rare technical term; the common word is 対空砲 (たいくうほう).
See also: 対空砲
対航空機砲 refers to the same thing as 対空砲, but is rarely used.
The standard, common term for anti-aircraft gun; 対航空機砲 is a rare synonym.
Compound of 対 (anti-), 航空機 (aircraft), and 砲 (gun).