Plain English Meaning
A lesson plan is practical when it can actually be carried out as written, given what the instructor and student really have to work with on the day.
Full Definition
In lesson planning, the quality of a plan being workable in the real conditions under which it will be taught — meaning it fits the time available, the resources on hand, the facilities, the weather, the aircraft, and the student's current ability.
Context Anchor
Seen when instructors build or review lesson plans for flight or ground training.
Derivation
From Latin 'practicus', meaning 'concerned with action or doing', as opposed to theory. A practical lesson plan is one built for doing, not just for reading on paper.