A programming language—or other tool, but I’m thinking about code right now—that includes a robust enough standard library that you can get useful work done with the default distribution. The quality of the batteries may vary, but they’re there.
Pretty subjective, really. Depends on what sort of tasks you need to get done, and may change over time. Say for example: nowadays a language that doesn’t have a built-in or standard library solution for JSON handling? I wouldn’t say it comes with batteries included.
Also also, a robust standard library is a common enough priority that the list of no-battery languages might be easier to compile. Zig maybe?
Anyways all this is a made up mix of opinion and marketing. If your toolkit fits your workflow, you’re good.
Contrast with Battery Pack.