Actually, all of you are wrong.
The Planet Earth is accurately described as an "oblate spheroid" and is neither round nor flat.
In common use, "round" is an alternative to "flat". Then it is either round of flat, by definition.
A circle is round, a ball is spherical.
I wonder what it is in 11 dimensions?
I thought we were up to 16 dimensions?
I thought it was 11 dimensions too - 4 'normal everyday' spacetime and rest curled up and invisible to us
Yes, that is one of the later models based on string theory and Brane theory of the universe.
One such theory is the 11-dimensional M-theory, which requires spacetime to have eleven dimensions, as opposed to the usual three spatial dimensions and the fourth dimension of time. The original string theories from the 1980s describe special cases of M-theory where the eleventh dimension is a very small circle or a line, and if these formulations are considered as fundamental, then string theory requires ten dimensions. But the theory also describes universes like ours, with four observable spacetime dimensions, as well as universes with up to 10 flat space dimensions, and also cases where the position in some of the dimensions is described by a complex number rather than a real number. The notion of spacetime dimension is not fixed in string theory: it is best thought of as different in different circumstances.