Quite a few questions that are about constant voltage or constant current sources are often incorrectly tagged with constant and either voltage or current. We already have constant-current (and theoretically constant-voltage) so I've fixed the tags on these questions. There are also a number of questions about time constants which were tagged time and constant instead of the correct time-constant, an issue which I also recently fixed and which I brought up years ago.
As it stands constant is only used on two more questions, and it is used in the context of VHDL / Verilog constants. I don't see much use for the tag on these questions, either, so I think it should be removed. That would leave it on 0 questions.
Furthermore, since the tag keeps re-appearing in various contexts we (1) can't just make it a synonym of a better tag and (2) will need to keep removing it as it is created over and over again. Thus, it seems to be a good candidate to be a blacklisted (i.e. blocked) tag. Or is there some type of question which it belongs on?