  We study the horizontal expansion of vertically confined ultra-cold atoms in
the presence of disorder. Vertical confinement allows us to realize a situation
with a few coupled harmonic oscillator quantum states. The disordered potential
is created by an optical speckle at an angle of 30{\deg} with respect to the
horizontal plane, resulting in an effective anisotropy of the correlation
lengths of a factor of 2 in that plane. We observe diffusion leading to
non-Gaussian density profiles. Diffusion coefficients, extracted from the
experimental results, show anisotropy and strong energy dependence, in
agreement with numerical calculations.
