large ball; giant ball
Often refers to a large ball used in school sports day events where teams push it, but can also mean any large ball.
There is an event at the sports day where they roll a giant ball.
The children pushed the giant ball toward the goal.
Compound of 大 (おお, 'big') and 玉 (たま, 'ball'). The reading おおだま is a straightforward combination.