A more thorough explanation:

Term: STR
Definition: An abbreviation for Suspicious Transaction Report, which is a document that financial institutions are required to file with the government when they suspect that a transaction may be related to illegal activity, such as money laundering or terrorism financing.
Example: A bank employee notices that a customer who has never made large deposits suddenly deposits $50,000 in cash. The employee becomes suspicious and files an STR with the government.
Explanation: The example illustrates how an STR is used to report suspicious activity to the government. Financial institutions are required to file STRs to help prevent illegal activity and protect the financial system from being used for criminal purposes.