An up trend is a price formation featuring a minimum of one or more higher lows and one or more higher highs (advancing). A down trend is a price formation featuring a minimum one or more lower lows and one or more lower highs.
Obviously time frame is an important consideration. A market might be trending up on a one minute chart, trending down on a 20 minute chart and consolidating on a daily chart simultaneously. In this way the market is fractal.