Definition of APL in US English:

APL

noun

Computing
  • A high-level programming language, typically used for mathematical computations.

Origin

1960s; earliest use found in Proceedings of the AFIPS Conference. Initialism from associative programming language, but now often explained as initialism from A Programming Language, the title of a 1962 book by K. E. Iverson, who devised the mathematical notation which was developed into the programming language.