(TSIYT-giyst)
(n.) The spirit of the time; the general outlook of a particular period or generation

It's from the German "Zeit," meaning "time," and "Geist," meaning "spirit." (The "geist" in "Zeitgeist," by the way, is a relative of the "geist" in English "poltergeist" and "ghost.")

"Ask any critic to comment upon this final year of the Century of American Music, and you're likely to hear a heavy sigh. The year 1999 gave us fluff and smut, the inflatable sweethearts of the teenage market and the foul-mouthed bullies of hip-hop and rock. Releases from aspiring legends like Nine Inch Nails, R. Kelly and Mary J. Blige failed to make the anticipated cultural impact, while previously dismissed artists like Limp Bizkit and Kid Rock rose to rule the Zeitgeist."--Ann Powers, writing in the New York Times.