WordNet sense 1 (curved or curving in and out):

sinuous

WordNet sense 2 (curved backward or inward):

recurvate, recurved

WordNet sense 3 (bent into or having an inward curve):

incurved

WordNet sense 4 (having curves):

curvy

WordNet sense 5 (curved like a sickle):

falcate

WordNet sense 6 (characterized by or following a curved line):

curvilinear

WordNet sense 7 (forming or resembling an arch):

arched, arcuate, bowed, bowed

WordNet sense 8 (having or marked by a curve or smoothly rounded bend):

curving