To fly over something.
My family planned to take pictures from the ground as I overflew them in the hot air balloon.
To fly too far past something.
The small size of the airstrip meant that pilots would frequently overfly and have to circle back.
To flow over the brim of (a container).
The river overflowed the levee.
To cover with a liquid, literally or figuratively.
The flash flood overflowed most of the parkland and some homes.
To cause an overflow.
To flow over the edge of a container.
The waters overflowed into the Ninth Ward.
To exceed limits or capacity.
The hospital ER was overflowing with flu cases.
To be superabundant; to abound.