Xandemic means: A period of time in the mid 2010s associated with widespread abuse of Xanax, an anti-anxiety medication, by teenagers in the United States.. It is internet-era slang, commonly seen on TikTok, Discord, Reddit or X. It touches on mental-health themes; if your teen uses it about themselves, a calm, non-judgemental check-in is worthwhile rather than a confrontation about the word itself.