There are currently four tags related to multidimensional arrays, lists, hashes, etc.
All these tags are related and should be merged into multidimensional-array. The multidimensional-array tag has the most questions (3367) and has an excerpt.
Maybe we should merge all these tags into multidimensional? That way it is clearer that lists, hashes, etc. are included in multidimensional. And as Some Helpful Commenter pointed out, the term multidimensional also applies to databases.
Multidimensional can refer to databases. E.g. this question
Seriously. Can we get this done?