Rubber Duck Test
Noun · Hacker Culture
Definitions
The practice of verifying a business idea, feature spec, or architectural decision by explaining it to someone (or something) uninitiated. If you can't explain it simply, you don't understand it yet.
In plain English: Explaining a business idea or technical plan to someone unfamiliar with it to see if it actually makes sense. If you can't explain it simply, you might not understand it well enough.