The cowl is the piece of metal from the base of the windshield wrapping into the engine compartment. In the photo above your post, the top of the cowl is the part painted black with the plastic grilles in it and the top part of the firewall, where the ignition module and wiper motor are mounted. If you look carefully, you can see that the line of sealer under the ignition module. That's the parting line between the cowl and the firewall.
