  Neutron scattering was used to determine the spin structure and the magnon
spectrum of the Mott--Hubbard insulator YTiO$_3$. The magnetic structure is
complex, comprising substantial G-type and A-type antiferromagnetic components
in addition to the predominant ferromagnetic component. The magnon spectrum, on
the other hand, is gapless and nearly isotropic. We show that these findings
are inconsistent with the orbitally ordered states thus far proposed for
YTiO$_3$ and discuss general implications for a theoretical description of
exchange interactions in orbitally degenerate systems.
