What does "ad indicem" mean in a citation?
To be short, yes.

According to the post in English.SE, it means 'see the index'. It basically tells you to refer the index section and look for the topic that is discussed in the context where it is cited.

Note: This question was asked in both Academia.SE and English.SE to benefit both communities as there isn't a single standard dictionary that could be found online to define this term. Credits go to the original answer in English.SE for answering my post.