What is an External Wind Baffle?

The built-in wing or lip on a vent to deflect the wind and enhance airflow.

The built-in wing or lip on a vent (a ridge vent, for example) that deflects wind up and over the vent creating the Bernoulli Effect that enhances airflow performance by pulling or lifting the air out of the attic. It also deflects weather elements over the vent away from the attic.