The web platform has evolved. Browsers are no longer just document renderers, they have become the most capable and ubiquitous application runtimes on the planet.
Right now, the most common term for applications that use the browser as a runtime is “Single Page App”. I’ve even heard people pronounce it like the word “spa”. If you’ve done this, we can probably still be friends :)
Personally, I’ve always disliked the term “single page app” because it fails to describe what my applications are. The fact that the app consists of a single initial HTML page is not what makes it interesting or unique. In fact, often times it’s plain wrong. A well-built “single page app” updates the URL as the user navigates around to different “pages” within the app, keeping their place if they refresh or share that URL. Perhaps at one time the “single pageness” was its defining characteristic, but these days the term makes it sound more like you’re building an application that doesn’t respect the URL and thus breaks the web.