What does "overflow" mean?

Additional senses

1. 2.To run over the bounds.
2. 3.To be superabundant; to abound. Rogers.
3. 4.A flowing over, as of water or other fluid; an inundation. Bacon.
4. 5.That which flows over; a superfluous portion; a superabundance. Shak.
5. 6.An outlet for the escape of surplus liquid. Overflow meeting, a meeting constituted of the surplus or overflow of another audience.