To hit in poker means to get a card, you need to improve your hand and likely end up with a winner.
For example, you’re holding a flush draw with AsKs, and you hit the turn as it comes 2s to complete your flush.
Hitting one of your outs when you know you’re behind is one of the best feelings in poker, but it’s important to stay calm and realize that now that the situation has changed, you need to figure out the way to make the most money possible.