Overextrusion looks droopy and stringy on prints. It happens when the hotend extrudes more material than necessary. It is caused by incorrect flow or extrusion multiplier settings in the slicing software.
This problem is somewhat similar to underextrusion in that incorrect slicing software settings could cause it.
Lower the flow setting: Setting the flow setting too high is a sure way to cause this.
Reduce the extrusion multiplier: It could also help to choose the proper extrusion multiplier level.