What's it all about?

It looks like we need to know what we all mean, around the world - here's a try at clarifying some confusions:

any messy substance used for messy pursuits. Usually quite liquid and by the bucketful. E.g. custard, porridge, wallpaper paste, soapy water, thin flour paste (batter). Can also be used to mean gunge
the same as slosh, really, but perhaps wider-ranging - I.e. any mucky substance used for application to a stooge. So custard is slosh, custard pies are gunge. Thick flour paste, dry flour, mud, tomato sauce, eggs, paint, etc..
originally the knockabout comedy used in theatre and then silent films, it's got messier over the years. Now more often means messy scenes, but still used to mean non-messy knockabout
take care, it might mean falling into the swimming pool fully, and beautifully, dressed, or it might mean diving, snorkelling, swimming, etc. or might mean the more intimate golden showers - that's right, 'pissing' about.