Geometric curve (8)
I believe the answer is:
parabola
'geometric curve' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for parabola that I've seen before include "Curve like path of object thrown in the air" , "Symmetrical curve" , "Kind of curve" , "(Mathematical) curve" , "Curve - Arab opal (anag)" .)