Wiktionary
insubstantially
adv. In an insubstantial manner.
WordNet
insubstantially
adv. lacking expression or fullness; "the finale of the symphony was played just a shade too fast and not quite insubstantially enough to convey the full, hollow horror of its implications"
Usage examples of "insubstantially".
Condensation was forming on the windscreen and the crane swung its skeletonic arm through the floodlights insubstantially, like a back projection on frosted glass.
She smiled at him and ghosted and he tried over and over again to grapple her while she shimmered insubstantially on the sidewalk.
They wavered in the runnels of water, wobbling insubstantially before sinking back down into the visitor’s core.