Operations
Grounding
Marking an aircraft as not available to fly - for maintenance, an expired inspection, or an open airworthiness-critical squawk.
In practice
The word is simple; the enforcement is what matters. A grounded airplane that still shows bookable on the schedule is an incident report waiting for a date. Well-run operations wire grounding into scheduling so the status change removes the airplane from the calendar automatically and notifies affected bookings - no reliance on every member reading the group chat.
See it with your own aircraft.
Add your aircraft and your rates, then see the schedule, the squawks, and the ledger all work off one record. No card required.