IPA: /ˈrɒtən/
KK: /ˈrɑtən/
In a state of decay or decomposition, often producing a bad smell; something that is spoiled or no longer good to use.
The fruit was left out too long and became rotten.
In a manner that is extremely bad or spoiled.
The child is spoiled rotten by his grandparents.
Rotten → It originates from Old English 'rotian' (meaning to rot or decay), which is related to the Proto-Germanic '*rōtōną' (meaning to rot). The word describes something that has decayed or decomposed, typically due to the action of bacteria or fungi.
Think of something that has 'decayed' ('rotian') — that's why 'rotten' means something that is spoiled or decomposed.