faults
Oxidation
No legal definition
Progressive reaction of whisky with oxygen in the bottle headspace, flattening aromatic top notes and building cardboard, stale and faintly sour characteristics. It accelerates as the bottle empties and headspace grows.
Not a legal term
No whisky regulation in Scotland, Ireland, the United States, the EU or Japan defines this. It is a trade or marketing term, so it is only actionable if its use is actively misleading.
Worth knowing
A bottle below about a third full changes noticeably within months, whereas a sealed full bottle can be stable for decades. Decanting into a smaller bottle is the practical countermeasure. Cask-strength whiskies generally resist oxidation longer than 40% bottlings.
Related terms
Last reviewed 2026-07-30 · All glossary terms