Windgegerbt is a compound adjective that literally means "wind-tanned" or "weather-beaten." It's a vivid and evocative word that paints a strong picture of someone who has spent a lot of time exposed to the elements, particularly the wind.
In the context of this sea shanty, it perfectly describes the rugged appearance of a sailor whose face has been hardened by the harsh conditions at sea. It's a less common word that immediately transports you to the maritime setting of the song.
Santiano put German words to Pink Floyd's "Wish You Were Here" and turned it into a sailor's song. The man singing it has already gone. He is "Wieder auf See" (back out at sea) with a photograph pressed against his chest, and the detail he keeps circling back to is a physical one: "Meine Lippen sind taub, taub von deinem Kuss" (my lips are numb, numb from your kiss). Not the memory of a kiss. The numbness it left behind.
The verse does the same thing with the rest of him. "Rau und hart meine Hände" (rough and hard, my hands), "Windgegerbt mein Gesicht" (my face weathered by the wind), a body worn down by the work, and then the line that turns it over: "Meine Seele war dunkel ohne dich" (my soul was dark without you). By the bridge even the weather has picked a side. "Der Himmel grau, die See ist trüb" (the sky is grey, the sea is murky), "Der Wind aus der falschen Richtung" (the wind comes from the wrong direction), and the ship leaves at dawn regardless. The chorus is enormous and shouted by a whole crew, and there is nothing in it he can actually do.