Definition
BEYOND VISUAL LINE OF SIGHT (BVLOS)
The operation of a UAS beyond the visual capability of the flight crew members (i.e., remote pilot in command [RPIC], the person manipulating the controls, and visual observer [VO]), if used to see the aircraft with vision unaided by any device other than corrective lenses, spectacles, and contact lenses.
Source: FAA Pilot/Controller Glossary (verbatim from the Federal Aviation Regulations).