A. Bryce, I think this is splitting hairs on the English definitions and missing the point of the French. Direct, simple translations are not always possible - each language has its own nuances that may not translate easily.

While ‘la piquette’ may not specifically mean ‘un vin bouchonné’, (bad as in off/spoilt), the French term covers all the English terms you mention, including ‘bad’ as opposed to ‘good’ wine. Drinkable, but not great, not good etc

However it is translated in English, the term is quite clear in French !