Tenner/ˈtenər/ Definition 1 of 3Pro Tip 1/3Slang Usage Used informally, may not be understood in formal situations or outside the UK. Next round is on me if you spot me a tenner. Pro Tip 2/3British Only Specific to British currency, wrong if used for other currencies. I need to break this tenner for change. Pro Tip 3/3Casual Transactions Commonly used in everyday transactions like borrowing or lending small amounts. Can I get a tenner off you for lunch?