The seizing of a person's property, credit or salary, on the basis of a law which allows it, and for the purposes of paying off a debt.
The person who possesses the assets of the debtor and is the subject of the seizure is called a "garnishee".
This is frequently used in the enforcement of child support where delinquent debtors will be subjected to salary garnishment.
A percentages of their wages is subtracted directly off their pay-check and directed to the person in need of support (the employer being the garnishee).
Also refered to as "attachment". For example, BC's Family Maintenance Enforcement Act, 2007, defines garnishment perfectly where is refers to an "attachment", at ¶24 (this is an extract only):
"If ... the court finds that a debtor who has defaulted in a payment required under a maintenance order is receiving or entitled to receive wages, salary or other remuneration from a person employing or engaging the services of the debtor, or is receiving or entitled to receive a benefit, the court must make an attachment order unless it would be unfair to the debtor to do so. The attachment order must direct a person who, either when the order is made or at any time while the order is in effect, employs or engages the services of the debtor or pays a benefit to ... deduct from the money or benefit due and owing and from time to time becoming due and owing to the debtor the amount required by the order...."