Basic semantic properties include being meaningful or meaningless – for example, whether a given word is part of a language's lexicon with a generally understood meaning
The "for example" being where it is, is confusing, and I believe should be left out.
I think this would have been better written as:
Basic semantic properties include, for example, being meaningful or meaningless (that is, whether a given word is part of a language's lexicon with a generally understood meaning); polysemy, ..