vomit -> vomiting

To consolidate the tags and aliasing into vomiting is consistent with the -ing preference.

Neither has a wiki and there's no reason both the action and object can't be tagged independently.

I agree that tagging the action and object separately could be useful, but the tags aren't currently used like that. A lot of images under vomit include people vomiting blood or flowers or something like that. Some cleanup and wiki definitions would be necessary, and even then I think people won't use the tags differently...

I don't think we can do this unless we are also willing to add a vomit_(object) tag, which seems excessive. I think clean-up and redefinition would be the best option. If the post contains literal expelled stomach contents (even in the absence of the action) it should be vomit as an object. The action, whether the subject is spewing stomach contents, blood, or flowers, would get the gerund form of the verb vomiting.

Noun and verb separate, like we did with pee/peeing.

There is currently only one image with the pee tag. The tag also has no wiki definition. However, peeing does have a wiki definition.

He probably meant urine instead of pee. And the aliases (urine -> peeing and pee -> peeing) were only removed recently (forum #82993), so neither urine nor pee have had the chance to be used much.