One who goes with the flow, no matter the surroundings. Can be used positively, for someone who can handle any situation. Also can be used as a pejorative, like someone who has no mind of their own and will just agree with whoever spoke last.
Ethan's a flowgoer, he's so chill even when we drag him along on our stupid "adventures"
God, that Ethan is such a tool and a flowgoer. Doesn't he have any opinions of his own?