Definition of "APL"

APL¹

noun
uncountable
1. (oncology, hematology) Initialism of acute promyelocytic leukemia.
  Quotations
  The disease that stood at the pivotal crossroads of oncology was yet another rare variant of leukemia called acute promyelocytic leukemia—APL.
  2010, Siddhartha Mukherjee, The Emperor of All Maladies, Fourth Estate (2011), page 407

APL²

proper noun
1. (astronomy, NASA, physics) Abbreviation of Applied Physics Laboratory (a Johns Hopkins University laboratory)
2. (physics, US) Abbreviation of Applied Physics Laboratory (at the University of Washington)
3. (computer languages) An early programming language using mathematically derived symbols for many of its operations.

APL³

noun
plural APLs
1. (scouting) Initialism of assistant patrol leader.