Final answer:
A reduction in a merchant's bank account by a credit card company due to a disputed transaction is called a chargeback. This is distinct from an overdraft, which is when an account goes negative due to spending more than the available balance.
Step-by-step explanation:
When a credit card company subtracts money from a merchant's bank account due to a disputed transaction, this is termed a chargeback. This is different from an overdraft, which occurs when an individual spends more money than is available in their account, often resulting in an overdraft fee. Unlike a chargeback, an overdraft represents a negative balance carried by the account holder, which can be costly.