1. denoting a lack of sight. See blindness.

2. denoting a lack of awareness. In research, a blind procedure may be employed deliberately to enhance experimental control: A single blind is a procedure in which participants are unaware of the experimental conditions under which they are operating; a double blind is a procedure in which both the participants and the experimenters interacting with them are unaware of the particular experimental conditions; and a triple blind is a procedure in which the participants, experimenters, and data analysts are all unaware of the particular experimental conditions.