Sludge, gunk, any fowl indiscernible substance actually (like stuff from a clogged sink). (so not actual crap, cause you know what that is)
Abstract it can mean crap, shit (as in crappy weather, I did shit on my exam) stinks, bad, failure
We do have the verb pruttelen, which is mainly used for the sound of a coffeemachine, but could also be used for an engine or, if it is em ... a serial fart... ow and soup boiling.
Basicly anything that sounds like many fast blublublublbub