I was looking through some of the questions today and it looks like some of the newly created tags are completely unnecessary, the lowpass-filter tag here, sinusoidal tag here, highpass-filter tag here and so on. Not all of them should be tags. There are more, and it's starting to look like we need to clean up. How do we do it and who has the privileges?
Yes, there is, using Tag Synonyms. To quote the page:
Alternatively, if there is a tag that is only used in 1-2 questions, simply retag it to something more appropriate, and the original will be deleted, eventually..
Lastly, if we bring a specific list of tags that need to be combined, and can all agree, a moderator could do it for us.