Scroll through the flashy websites of neurotechnology startups and a phrase repeats again and again: “minimally invasive.”

“The term is fuzzy, problematic,” said Anna Wexler, a medical ethics and health policy professor at the University of Pennsylvania Perelman School of Medicine. “Is it physical invasiveness? We’re not sure, it’s a fraught term.”

The fuzziness hasn’t stopped most brain-computer interface startups from deploying it in a bid to differentiate their devices from others in development. Synchron, Motif Neurotech, Precision Neuroscience, and Merge Labs all use it liberally. Journalists sometimes repeat the spin.