Urinating eliminates waste that would harm the body. In dreams it symbolizes the need to eliminate an issue from the past or a negative influence in the present. For example, to dream of urinating in the shower while your partner enters and leaves the shower or bathroom is a request to eliminate the negative influence of your partner leaving you. It can also mean you need to (deal with) eliminate the aspects of the relationship that invade your personal space. To urinate in the back of a pickup truck is a request to eliminate the negative influence you picked up from your father (truck) in the past (back of truck).