The Collaborative International Dictionary
Overproof \O"ver*proof"\, a. Containing more alcohol than proof spirit; stronger than proof spirit; that is, containing more than 49.3 per cent by weight of alcohol.
Wiktionary
a. Possessing a higher proportion of alcohol than proof spirit. Sometimes abbreviated to OP.
Wikipedia
Overproof is the first full-length album by the American hip hop duo Substance Abuse. The Los Angeles-based group have garnered much acclaim following the release of the album, particularly for its incorporation of legendary MC Kool Keith and the ever present MF Doom on the songs 'Night On The Town' and 'Profitless Thoughts' respectively. The album received four stars in URB and Scratch Magazine.
Usage examples of "overproof".
He was trying not to think about how it got there, and he figured the overproof would help.
As Jack ran for the doors, the bottle of overproof slipped out of his pocket and smashed on the concrete.