People who enjoy standing and watching (without actively participating in) an activity.
Look at that crowd of gongoozlers in front of the new showroom! Don't these people have any other work, than to stand and stare?
A person who idly watches the labours of others while declining to offer assistance or becoming involved. Traditionally a term used by canal bargees when referring to onlookers found clustering around locks and moorings where barges have to stop and the crew engage in sometimes hard physical activity to make progress.
"Don't stuff up at Five Rise Locks or you'll get a cheer from the gongoozlers"