A "do-while" loop is a control structure used in programming that allows a block of code to be executed at least once before checking a condition. This means that the code inside the loop runs first, and then the condition is evaluated. If the condition is true, the loop continues; if false, it stops. The syntax of a "do-while" loop typically includes the keyword do, followed by the code block, and then the while keyword with a condition in parentheses. This structure is useful when you want to ensure that the code executes at least one time, regardless of the condition.