The Jolly Roger was a pirate flag.
There is no direct translation for the phrase for he is a jolly good fellow. The closest German translation would be denn er ist ein famoser Kerl.
Was ist ein Film = What is a film
Was ist ein Sediment = what is a sediment
Was ist ein Haussperling = What is a house sparrow
Was ist ein Schnabeltier = What is a duck-billed platypus
Was ist ein Deich = What is a dyke/levee/embankment
Was ist ein weißer Kuss - What is a white kiss
No, a jolly roger is a pirates flag.
er ist ein = he is a... (sentence fragment)
The Jolly Roger was the flag, not the ship. Jolly Roger refers to flags flown on ships which identify the ship's crew as pirates. So, pirates sail with the Jolly Roger flying. The most common Jolly Roger is the skull and crossbones.
Jolly roger
Ein Komet is a comet.