(a.) Undulating.

alternate beating bent billowing billowy circling curvaceous curvate curvated curve curved curvesome curviform curvilineal curvilinear curving curvy cyclic epochal even every other geosynclinal incurvate incurvated incurved incurving intermittent isochronal labyrinthine mazy meandering measured metronomic oscillatory periodical pulsing reciprocal recurrent recurring recurvate recurvated recurved recurving rhythmic rolling rotary seasonal serial serpentine sinuous steady surgy tortuous undulate undulated undulating undulative undulatory wavelike waving wavy wheeling