Indirect light means no direct sunlight. Very bright indirect light would mean shade but open to the sky, not hidden under a big beech tree or stuck in a dark alley.

Almost any artificial light would be considered indirect since it is unlikely to rival direct sunlight. Make sure that you reflector does not produce hotspots of very intense light that could burn the plant. That means avoiding completely smooth reflectors and looking for one with an uneven surface. A simple white reflector instead of a shiny one is perfectly good for this. You can also look to surround the plants with white surfaces on all sides so that light reaches the plant from all directions instead of just directly overhead.

Thank you.