When listening to Space Shuttle countdown I notice the endings "and counting" and "and holding". I can imagine what "and counting" means, but what is "and holding"? Countdown has stopped? Why?
Shuttle launches clock a countdown from T-43 hours (i.e., 43 hours before liftoff) to T-0 (liftoff). The clock is important, not just to watch the time go by, but because dozens of activities are keyed to it. For example, at T-2 minutes, the crew knows to close and lock their visors, and at T-6.6 seconds, they ignite the engine. For details go here.
If things are going smoothly, the clock runs and is said to be counting. If there's a problem, flight control stops the clock, and it is said to be "holding," from its meaning of grasping and not letting go.
"The ship is up to 5000 meters and holding, sir"
The ship has reached 5000 meters and is sustaining this altitude.