In cryptocurrency, pump is a signal or a sign to investors that they crypto market will rise and good investors will buy hold,while dump is a signal that they values will fall significantly
There are diverse concepts in the market. Among them all, a pump which is a sign of price appreciation is a desirable state to hold the coins and try to invest up to the limit your budget can allow you. In dump, many people might stay away from the market but that is normally the good time to invest because you can buy many coins with a little money and this is what maximizes your utility in future.