Could mean a lot.
1: Idle screw could just be set way to low.
2: If you have a fuel filter in may be clogged.
3: Fuel pump pressure could be low and the vacuum of the engine in sucking the fuel in.
4: May be a clogged line or a crake in the line.
5: carb could be sucking in air or have a leak.
Question? What engine are you running and what carb? If your not sure post a photo. The folks around here can identify it and help you out.
