I wouldn't worry about how **many** undefined tags we have - instead focus on making sure that the top-used tags* (tags covering ~90% of questions) have tag wikis (and excerpts) that are *meaningful* and describe not only *what* the tag represents, but *when* the tag should be used as well.

Of course, if you're in the mood and feel like creating some lesser-used tag wikis, go right ahead!

<sub>* which incidentally is how the [Tags][1] page is sorted by default</sub>

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To address concerns about tag misuse:

Don't get hung up on tag definitions as a 'silver bullet' way to solve the mistagging issues. Generally, people who tag incorrectly do so because they **don't bother reading the tag definition**. 

A current example of this is the [msi][2] tag, which the tag definition clearly stated that this was for the windows-installer filetype `.msi`, **not** for the company of the same acronym who produces computer hardware. Yet a lot of its uses were for the latter. (It was cleaned and synonymised with [tag:windows-installer] in the end)

What we **should** be focusing on instead is *reducing ambiguity in our tags*. Ambiguous tags lead to tag misuse - **even with a tag definition**. 

We can do this by:

- Using full names in our tags (where possible)
 - Avoiding acronyms or shortened names. 
- Avoiding tags with multiple meanings 
 - For example: Instead of tagging with [tag:command-line], we should tag with the specific terminal-program (powershell,bash,windows-command-prompt)
- Being explicit in the wording of our tags 
 - e.g. Instead of just [tag:power], we should use [tag:power-supply]
 - Instead of [tag:vlc], we should use [tag:vlc-media-player]
- Removing obvious meta-tags. 
 - These are tags that are subjective, like 'beginner' (beginner according to what criteria?), and describe the person or the question, not the problem/topic at hand.

  [1]: http://superuser.com/tags
  [2]: http://meta.superuser.com/q/8166/107240