No Outlet sign
The street or network of streets ahead has no through connection to another road, even though it may branch and wind for some distance first. Everyone on it eventually has to turn back.
Federal designation W14-2 in the MUTCD, the national standard every state signs to. Common at the entrance to residential subdivisions built around loops and cul de sacs that never connect back to a through road.
How to recognise it
This sign is a diamond stood on its point in yellow, the warning colour. Yellow diamonds telling you what the road is about to do. They are advisory rather than mandatory, but ignoring them is how people end up in ditches and how examiners end up failing you.
What the test wants you to know
The distinction from Dead End is scope: No Outlet warns that a whole network of connected streets, loops and cul de sacs ahead all fail to reconnect to a through road, not just the one street you are on. Read it as information about the layout ahead, not as an instruction to stop where the sign stands.
The sign people confuse it with
No Outlet gets mixed up with Dead End more than any other pairing in this category. Put them side by side and the difference is obvious, which is exactly why it is worth doing once rather than meeting them cold in the exam.
Practise it
Reading about a sign is not the same as recognising it in half a second with an examiner watching. Every state road signs test on this site shows the sign and asks you to name it, then shows four faces and asks you to pick the right one.