Floor lamp loose at base

You can attempt to use thread seal tape also known as PTFE or plumber's tape. It's the white malleable strip that is used for plumbing seals - see wiki: https://en.wikipedia.org/wiki/Thread_sea...

By adding some to the screws, it can help tighten the gap caused by the stripped threads. However, depending how bad it is, this might not be enough. Adding a super strong glue along with the seal tape is a good addition to permanently fix the problem. - Just make sure to test fit with some seal tape before ever adding glue to ensure that the screws fit snugly. Adding too much seal tape causes it to bind up, so test fitting first will help you determine how much you need per screw.

Another solution is to attempt to use a screw that is just so slightly bigger to cause enough friction and hold. Again, not a perfect solution, because it may be impossible to screw it completely down, causing a ugly screw to stick out.

A final idea is to use a wood shim cut to the right size to replace the screw altogether.