The fraudulent appropriation of someone's identifying or personal data or documents, such as a driver's license, social security number (in USA), medical records, credit cards, etc. and then using that information to fraudulently procure goods and services essentially trading on the victim's good name.
TOM: "I had a job interview. They couldn't hire me because I had just been fired after working there for two years. Rather, the identity thief
was hired there using my social security number and name to pass the background check. Now the state is after me to pay back the welfare benefits he got after losing his, er... my job."
PHIL: "Yeah? FBI raided my house and took my computer because someone opened a child porn website using my name, address, and credit card information."
BOB: Hospital almost gave me a lethal dose of insulin because the identity
thief who stole my identity was diabetic so it showed up in my charts that I was diabetic. Thank goodness the doctor tested me first.
TOM: "Dang, remember when identity theft only took your credit cards and drained your bank account."