This is another of those winemaking terms you see on a bottle's back label. It simply means that the wine has been aged in the bottle, presumably to let it mature and develop. Most wineries age their wine in the bottle anywhere from a few weeks to several years. Fine wines, particularly reds, may need further aging once they're passed on to the consumer, though the majority of today's wines are made to be drunk shortly after release. See also aging and barrel-aged.