Plain English Meaning
It is the work an instructor does to get better at being understood. You practice explaining things, check whether the learner actually got the message, and keep adjusting your words, examples, and delivery until your teaching reliably lands.
Full Definition
The deliberate, ongoing process by which an aviation instructor improves their ability to transmit ideas, instructions, and feedback to learners clearly and effectively. It involves practicing the four basic elements of communication — source, symbols, receiver, and meaningful experience — and refining each through study, role assumption, accurate content, organized thought, and continual self-evaluation.