From malware.news
cross-reference, n.
A reference or direction in one place in a book or other source of information to information at another place in the same work
(from Wiktionary)
To help you during analysis, IDA keeps track of cross-references (or xrefs for short) between different parts of the program. You can inspect them, navigate them or even add your own to augment the analysis and help IDA or the decompiler.