Plain English Meaning
A taxonomy is an organized list that sorts things into groups and levels. In flight training, it usually means a step-by-step ranking of learning goals, from simple recall up to higher-level thinking and decision-making.
Full Definition
A structured system of classification that arranges items, ideas, or learning objectives into ordered categories, usually from simpler to more complex. In aviation instruction, the term most often refers to a taxonomy of educational objectives — a framework that organizes levels of learning (such as knowledge, comprehension, application, analysis, synthesis, and evaluation) so instructors can plan, teach, and measure student progress in a consistent way.