  The $C_{2v}$ symmetry of the W(110) surface influences strongly the
spin-polarized Dirac-cone-like surface state within a spin-orbit-induced
symmetry gap. We present a detailed angle-resolved photoemission study with
$s$- and $p$-polarized light along three different symmetry lines. The
Dirac-cone-like feature appears along $\bar{\Gamma}\bar{H}$ and
$\bar{\Gamma}\bar{S}$, while it is strongly deformed along
$\bar{\Gamma}\bar{N}$. A two-fold $\Sigma_{3}$ symmetry of the $d$-type surface
state is identified from photoemission experiments using linear polarized
light. Our results are well described by model calculations based on an
effective Hamiltonian with $C_{2v}$ symmetry including Rashba parameters up to
third order. The flattened Dirac cone of the surface state is caused by
hybridization with bulk continuum states of $\Sigma_{1}$ and $\Sigma_{2}$
symmetry. The spin texture of this state obtained from the model calculations
shows a quasi-one dimensional behavior. This finding opens a new avenue in the
study of $d$-electron-based persistent spin helix systems and/or weak
topological insulators.
