  We report the single-crystal growth and the fundamental magnetic and
thermodynamic properties of a rare-earth triangular lattice antiferromagnet
CeCd$_3$As$_3$. In this rare-earth antiferromagnet, the Ce local moments form a
perfect triangular lattice. Due to the spin-orbital-entangled nature of the Ce
local moments, the compound exhibits extremely anisotropic antiferromagnetic
couplings along the c direction and in the ab plane respectively. We show that
CeCd$_3$As$_3$ represents a {\it rare} experimental realization of an
antiferromagnetic Ising model on a two dimensional triangular lattice and thus
provides a prototype example for geometrical frustration. We further discuss
the quantum effect of the perturbative interactions on the top of the
predominant Ising interaction.
