What is the meaning of the continous line under the weld symbol. I have seen dashed line under the symbol but ıt is the first time i saw a continous line.
It would probably be a grind flush flat finish (though a machined finished should have an "M", Grinding a "G", and chipping a "C") with a V prep.
Oddly, the curved implies a concave finish, though almost always a convex (raised) curve is allowed/required so the weld finished surface after grinding or machining does not reduce the effective final wall thickness. (Perhaps a concave surface is needed for a sliding or a clearance fit, when any raised piece will cause an interference with a future part or assembly? )
It's definitely a welding related symbol. It looks to me like it would indicate a 1-sided V-groove weld. The double line indicates the other side is the EOP and the curve on top indicates the weld material is to be concave.
The root of the groove weld is finished flush and the face of the groove weld is specified as concave. Both, because no method of mechanical finishing is specified, is as welded. The contours are preferences. As noted in one of the other responses, had there been a letter adjacent to the flush symbol or the concave symbol, it would indicate the method of achieving the required contour.