1. [late 19C+] complete, utter.
2. [20C+] a negative intensifier, e.g. not a blind bit of use, not a blind word, not take a blind bit of notice.
3. [1940s+] (bingo) the round numbers from 20 to 80 in multiples of 10, e.g. blind 30, blind 20 [the 0 on the end].