The most useful definition of price action for a trader is also the simplest: it is any change in price on any type of chart or time frame. The smallest unit of change is the tick, which has a different value for each market. Incidentally, a tick has two meanings. It is the smallest unit of change in price that a market can make, which for most stocks is a penny. It is also every trade that takes place during the day, so each entry on a time and sales table is a tick, even if it is at the same price as the prior trade. Every time the price changes, that change is an example of price action. There is no universally accepted definition of price action, and since you always need to try to be aware of even the seemingly least significant piece of information that the market is offering, you must have a very broad definition. You cannot dismiss anything, because very often something that initially appears minor leads to a great trade.
The definition alone does not tell you anything about placing a trade, because every bar is a potential signal both for a short and for a long trade. There are traders out there who will be looking to short the next tick because they believe that the market won't go one tick higher and others who will buy it believing that the market will likely not go one tick lower. They might be looking at the same chart and one trader sees a bullish pattern and the other thinks there is a bearish pattern that is stronger. They might be relying ...