What does open hot outlet mean?

An open hot reading on your outlet tester means that the wire that should be 'hot', or connected to power, isn't getting any power. There could be a couple of reasons for this. If the outlet reading as open hot is connected to a switch, the switch could just be in the off position. However, if the outlet isn't connected to a switch or the switch is on, then the hot wire has disconnected somewhere. Having a disconnected or intermittently connected wire can be a fire hazard, and should be looked at by an electrician.