curvilinear
Concise Oxford English Dictionary © 2008 Oxford University Press:
curvilinear /ˌkəːvɪˈlɪnɪə/
▶adjective contained by or consisting of a curved line or lines.
– derivatives
curvilinearly adverb.
curvilinearly adverb.
– origin C18: from L. curvus ‘bent, curved’, on the pattern of rectilinear.
'curvilinear' also found in these Oxford entries:

