@supinf Raise a flag on one of the downvoted questions. In all likelihood, the votes will be reverted, but by raising a flag, you make us aware of the problem.
Thank you @XanderHenderson I did as you suggested and flagged one of the downvoted questions. Since there are multiple accounts involved i am not sure if the automated serial downvoting detection will notice.
I do not care so much about my reputation, as it can be regained easily. but this kind of behavior is not healthy for MSE in my opinion.
@Integrand I have seen that you was active in some discussions on meta and on main related to tags. I just wanted to point out that there is also Tagging chatroom. Admittedly, it is not very active - but it might be good to know that it exists.
Of course, in this case help from moderators will be needed to approve the synonym you've mentioned. (And in general, it is rather difficult to get synonyms approved by voting, most of them are created by moderators.)
As far as I can tell, only 26 synonyms have been approved without any moderator intervention: https://data.stackexchange.com/math/query/1241631/synonyms-approved-by-non-moderators
@XanderHenderson I noticed that a majority from the downvotes from that incident were reversed, and that I got a majority of the lost reputation back. Thank you for looking into it and for keeping this site a good place!