Screen Door
Noun · Slang & Abbreviations
Definitions
A metaphor for protection or structure that is too flimsy to do the job expected of it. In engineering slang, calling a safeguard a screen door means it may look like a boundary while letting the important stuff right through.
In plain English: A weak barrier or control that does not really stop what matters.
Example: "The input validation was basically a screen door, blocking only the most obvious bad cases while letting malformed state through in slightly different shapes."