IPA: //ˈoʊvərˌpruːf//
KK: /ˈoʊvərˌpruf/
Having a higher alcohol content than the standard proof level, typically more than 50% alcohol by volume.
The bartender recommended a cocktail made with overproof rum for a stronger flavor.
Overproof → It is formed from "over-" (meaning excessively) and "proof" (from Old French *profe*, meaning to test or prove). The word "overproof" refers to a spirit that has a higher alcohol content than the standard proof, indicating it has been tested to be excessively strong.
Think of something that is 'excessively' strong ('over-') and has been 'tested' ('proof') for its alcohol content.