Definition:
Picking bottoms in forex trading means to try to take a guess on where a currency pair will stop falling and will begin to start rising.
This practice is common with beginning traders because they have not learned to beat the need to be right on a currency prediction.
Picking bottoms, or tops for that matter, is a risky business and can lead to the ruin of a trading career. It's best to stick with following trends until their end is confirmed. If you truly believe that you are selling into a bottom, just wait it out, or set a reasonable stop.