It means the light modifier is designed to set up quickly, like an umbrella. Instead of assembling rods and panels like a traditional softbox, you typically just open it and use it right away.

In practice, this usually refers to an umbrella-style softbox or umbrella/softbox hybrid: it opens with an umbrella mechanism but includes a front diffuser panel so it behaves more like a softbox. The main benefit is faster, simpler setup and teardown.

So yes, it’s partly marketing language, but it does describe a real design feature: quick umbrella-style deployment with softer, more controlled light than a bare umbrella alone.