A "problem without words" is a problem where no stipulation
is given, most often because the problem solves itself.
It is only interesting because something remains implicit. Often this
can only be discovered through retrograde analysis. Then one soon sees
that e.g. there is only one possible future course of action.
Here is an example:
K. Fabel and W. Keym
Basler Nachrichten, 1967
13+3. Problem without words
No stipulation is given, but a simple analysis of the position (see
full solution) shows that White just played g2-g4, so that
Black has the move and has no choice but to give mate with f4xg3 ep.
Who needs more directions?