This is a reference used to define many conditions that is usually negative in its terminology. For instance, if your car goes straight up the bank, it is not in the slot which is not good. If you car hits the glue zone and goes straight up it is not in the slot which is not good. Another use for the term is when you are running group 7 and disconnect your choke to run the power "straight up". Usually this condition will cause your car to leave the slot which is not good, or it will cause smoke to pour straight up out of a car sitting very still but still in the slot. You guessed it, a condition which is not good.