COMSS Boot USB for Windows isn[SQ]t a standard or widely known term or piece of software. There[SQ]s no official Microsoft tool or commonly used third-party utility with that exact name.

It[SQ]s possible that :

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It[SQ]s a custom-created tool:

Someone or an organization might have created a bootable USB drive and named it "COMSS Boot USB." The name "COMSS" likely refers to an internal abbreviation or project name within that organization. Without more context about where you encountered this term, it[SQ]s impossible to say what it is.
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It[SQ]s a typo or misspelling:

There[SQ]s a chance the name is slightly incorrect, and it[SQ]s similar to another tool. Could it be a variation on a different acronym or name?
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It[SQ]s referring to a specific company[SQ]s imaging process:

Some companies create custom bootable USBs for deploying Windows images to their systems. "COMSS" might be a company[SQ]s internal identifier for this process.

To find out what it is, you[SQ]d need to provide more information, such as:

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Where did you see this term?

(Website, document, conversation)
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What is its purpose?

(What is it supposed to do?)
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Do you have any more details about the source?

With more context, it might be possible to identify what "COMSS Boot USB for Windows" refers to.