hypercycles
... that, in hyperbolic geometry, hypercycles are curves with constant distance from a straight line but are not themselves straight?
... that, in <a href="./Hyperbolic_geometry" id="mwAno" rel="mw:WikiLink" title="Hyperbolic geometry">hyperbolic geometry</a>, <b id="mwAns"><a href="./Hypercycle_(geometry)" id="mwAnw" rel="mw:WikiLink" title="Hypercycle (geometry)">hypercycles</a></b> are curves with constant distance from a straight line but are not themselves straight?