The **bundle‑loader** is a now‑deprecated Webpack loader that lets you import a file ending in `.bundle.js` as a lazy‑loaded chunk. It wraps the module in a `require.ensure` call, returning a function that invokes callbacks once the generated chunk is fetched, and supports options for lazy loading and custom chunk names. It was aimed at Webpack users needing on‑demand code splitting before native dynamic `import()` became widely used.