As near as I can make out Blind Survey refers to a Survey that is not a set of aimed observations of previously known objects (galaxies, stars, clouds), but is attempting to discover unknown sources and/or gather statistics that avoid some of the inevitable bias.
Such a survey often covers a pre-chosen region of the sky, and Deep Surveys often fit the description. It may cover a larger Survey Field, even to the extent of being labeled All Sky, but there are obvious trade-offs regarding Angular Resolution, signal strength, Wavelength's covered, and amount of the Celestial Sphere covered.
Some surveys termed "blind" aim at a specific volume, e.g., the Milky Way, or a Redshift range, and/or aim at a specific phenomena, such as Pulsars, or the 21cm Line at different redshifts. Some Transient surveys have been described as "blind", and the term seems to fit many of them.
Australian Square Kilometre Array Pathfinder (ASKAP)