The outline of a thing seen from the side. A shape drawn by its edge alone, showing what a full view would hide.
Italian profilare (to draw in outline), from pro- (forward) + filare (to spin a thread), from filum (thread); a profile is, by its root, a line drawn as if with a single continuous thread.
The outline of a thing as seen from one side, which shows some things and necessarily hides others. What a profile leaves out is not a flaw in it — an outline was never meant to be the whole shape.