In orbitally degenerated triangular system it is predicted that orbital ordering and associated local magnetic trimerization to remove frustration. In BaV10O15 lattice trimerization possibly originated from orbital ordering was observed by synchrotron x-ray experiment. Next step is to observe the magnetic trimerization that can be detected as dispersionless excitation at hw=100-200 meV. Here we propose to perform inelastic neutron scattering in BaV10O15 to reveal the nature of geometrically frustrated system with orbital degeneracy.