The term 'single-page application' (SPA) in web development refers to a web application that loads a single HTML page and dynamically updates content as users interact with the app. SPAs enhance user experience by providing fast loading times and seamless interactions reminiscent of desktop applications. Technologies like AJAX and frameworks such as React or Angular help facilitate SPAs, allowing for smooth transitions and reduced server requests. By minimizing reloads and focusing on the client-side, SPAs enhance performance and deliver a more fluid, engaging experience for users.