What's the meaning of "out" in "build out"?

Question

From NPR

Critics suggest these big ISPs aren't building out their networks enough to keep pace with the huge growth in demand.

I haven't found the definition of "build out" in the dictionary, so I looked "out" up, and find the following definition:

out: used to say that something is done carefully or completely

And examples about the usage:

I spent all morning cleaning out the kitchen cupboards.

In the summer months the soil dries out quickly.

I want to know if "out" fit in with the definition. And I guess "build out" means "build carefully and completely", doesn't it? Because I have encountered the expression twice, I want to know the exact meaning, but I cannot find it on the Internet or dictionary.

Answer 1

That's an interesting phrase.

"Building out" in this sense probably means growing, spreading out.

And I guess "build out" means "build carefully and completely", doesn't it?

I don't think so, although it could. Given the context, it sounds like internet providers are trying to expand their properties to compete, and not necessarily to finish a specific project or directive. It just looks like a conjoining of "building" and "spreading out". If I were talking about a project, although it would sound extremely unusual, I could say "We're about to build out that particular phase", and the person I was talking to could probably get the idea, although I would much more likely say "We're about to finish out that particular phase" or "complete".

Answer 2

I encounter this phrase quite a bit in the tech sphere, where it indicates that an undeveloped project will be taken from ideation to implementation.

Similar to “filling out”, “building out” can certainly involve physical expansion, but can also be used more abstractly to indicate that something will be solidified, realized (sense 3), or generally developed—usually completely, as you surmised.