“4-D” can mean different things depending on context:

• 4-D (four-dimensional): something described using four dimensions, usually 3D space + time (used in physics and mathematics).
• 4-D movies/experiences: films or attractions that add physical effects (like seat movement, wind, water, smells) to a 3D movie.
• General usage: sometimes used loosely to mean something “extra immersive” or “beyond 3D.”

In short, 4-D = 3D plus an additional dimension or sensory effect, depending on context.