Curvilinear

The curvilinear roof gives beauty to the design as well as affording more head room inside than the ordinary straight rafter.

If a curvilinear triangle has for its sides arcs of circles which if produced would cut orthogonally the fundamental plane, the sum of the angles of this curvilinear triangle will be less than two right angles.

the curvilinear motion of a thrown stone

In early art rectilinear decoration marks an advance on curvilinear, which, in the long ages before pottery was thought of, would naturally be associated with the fibrous baskets that served as vessels.