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 particular 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.