I know the term deliberate practice is the current buzzword but I don’t think it is getting the job done. Words create images and images create action, so I use the term meaningful. Meaningful clearly communicates what I want from practice, it leaves little room for nuance. Practice must have a clear plan and purpose that the athlete understands. It must relate to the competitive demands of the sport the athlete is preparing for. It must be relevant to physical and developmental age of the athlete (Adult drills and training methods imposed on children are counterproductive).
Mindless repetition does not count as practice. If you want examples go watch a typical tennis academy practice where they hit balls for four hours or watch a baseball infielder take 100 ground balls repetitively. That is the norm just look around, nothing meaningful, just work. Each drill, each exercise must have a purpose that the athlete clearly understands or it is just time on their feet punching a clock accumulating time toward that magic 10,000 hour number. Focused meaningful work that chooses to distort the competitive demands not replicate them is the answer. That is meaningful, the athlete relates to it because they see the relationship of the technique they must master or the game situation they must improve. At the end of the day less is more to make the practice meaningful.