SiFive: Design and produce custom RISC‑V CPUs and SoCs (opens in new tab)

That's what "fabless" about means. I think using it as an attribute to the chip it's a misapplication of the term. Many companies today don't own chip fabrication plants, so that's kind of the norm, apart from IBM, Samsung and Intel. For instance the new Ampere ARM processor is manufactured by TSMC.

Back in the 80s it was the norm for chip design companies who produced their chips in high volumes to own their own fab. As the price and complexity of fabs went up they've mostly switched to outsourcing their fabrication to take advantage of economies of scale (since the fab equipment, which costs hundreds of millions of dollars for cutting-edge nodes, can be shared), hence "fabless".

Many, if not most, chip companies are fabless these days, including the very major ones (Broadcom, Qualcomm, Nvidia, etc. I think even AMD).

It means that they do not own any foundry/factory to produce chips.

They design chips then send the designs to a third party foundry for production, like you would perhaps do for PCBs.

There are only 4 companies that make chips anymore, at least at the latest CPU technology.

GloFo (serving IBM and AMD), TSMC (Serving Apple, NVidia), Samsung (serving Qualcomm, Samsung), and Intel (serving themselves).

GloFo ran out of money this year however, and will no longer compete with the high-end. Forcing AMD to make their next generation chip on TSMC.

Memory makers are their own market, and are ignored (ex: Micron).

---------

Fabless just means you send your chip designs to one of these fabrication labs (TSMC or Samsung... since GloFo is now out). And its TSMC or Samsung who makes the chips for you.