What does this "engineering symbol" mean?

That looks something like the symbol for a reversible hydraulic motor, but I don't think the triangles should meet in the center of the circle. Hydraulic input and output connections would be drawn as lines outside the circle connected to the bases of the triangles. A rectangle representing a motor shaft might be drawn to one side extending from the circle outward. Since engineering drawings are not drawn in color, schematic diagram symbols are usually seen only in black and white. The little wrinkles on the circumference of the circle at the corners of the triangles are not likely to be included in a schematic symbol. At the size such symbols are usually drawn, they would not be legible.

The schematic symbol for a gate valve is two triangles (outline drawn only) with points meeting but without a circle.

The excavator shows hydraulic cylinders that move the parts, so a hydraulic symbol would be somewhat related to the product.

It means absolute value, so no matter what the value of x is, positive or negative, this symbol makes it positive.

so if x is 7, y = 7 and if x = -7, y still equals 7

Hazard symbol earth working in progress

just a symbol and mean nothing to me