From English - German Ding/FreeDict dictionary ver. 1.9-fd1:
flat cap /flˈat kˈap/
Schiebermütze <fem>, Batschkapp <fem> [Hessen] [ugs.]
see: cap, soft hat, hat, caps, soft hats, hats, bathing cap, bobble hat, bobble, pom-pom, pom-pon, folding hat, field cap, nightcap, fur cap, baseball cap, baseball hat, peaked cap, yachting cap, knitted hat, knit cap, beanie cap, beanie, student cap, coonskin cap, wollen hat, woolly hat, balaclava, stocking cap, cable hat