Definition of "slimeball"
slimeball
noun
plural slimeballs
(biology) A round lump made up of or coated with slime or a slime-like substance such as mucus.
(helminthology, specifically) A mucus-coated lump containing the cercariae (“parasitic larvae”) of a liver fluke (of the phylum Platyhelminthes).
Quotations
The eggs [of a lancet fluke (Dicrocoelium dendriticum)] that pass out with the manure of an infested sheep do not hatch in the open. When eaten by the snail, they hatch and finally give rise to larvae that pass out of the snail's body in gelatinous "slime[-]balls."
1957 May, J[ohn] T. Lucker, A. O. Foster, “Adult Tapeworms”, in Parasites and Parasitic Diseases of Sheep (Farmers’ Bulletin; no. 1330), Washington, D.C.: United States Department of Agriculture, page 38
The cercariae contain massive glands, formerly considered to be penetration glands, but now believed to produce the slime responsible for the formation of these balls. It is likely that the slime produced by the snail itself may contribute, at least partly, to the formation of a slimeball.
1976, J[ames] D[esmond] Smyth, “Digenea: Bucephalidae, Fasciolidae, Opisthorchiidae, Dicrocoeliidae”, in Introduction to Animal Parasitology (Biological Science Texts), 2nd edition, New York, N.Y.: John Wiley & Sons, page 181, column 2; 3rd edition, Cambridge, Cambridgeshire, New York, N.Y.: Cambridge University Press, 1994, page 215, column 2
These flukes have three hosts. [...] As the infected snail crawls along it leaves slime balls containing cercaria on grass. An ant, Formica fusca, the arthropod host for D. dendriticum in the United States, is infected when it ingests the slime balls. Mammals are infected by consuming ants containing encysted metacercaria.
1995, A. M. Marty, E. M. Andersen, “Helminthology”, in Wilhelm Doerr, Gerhard Seifert, Erwin Uehlinger, editors, Tropical Pathology (Spezielle pathologische Anatomie: Ein Lehr- und Nachschlagewerk [Special Pathological Anatomy: A Teaching and Reference Work]; 8), 2nd edition, Berlin, Heidelberg: Springer-Verlag, page 827
(originally US, colloquial, derogatory) A person who is regarded as slimy (that is, sneaky or underhanded) or otherwise undesirable.
Quotations
And I put my hands on her jugs. She goes crazy. She says 'Take your hands off me slimeball!' So I go, 'Rona, watch your language!' And she goes, 'If you wanna have fun with your hands, why don't you pass the time playin' solitaire.'
1993, John Lahr, The Manchurian Candidate: A Play [...] From the Novel by Richard Condon, New York, N.Y.: Dramatists Play Service, page 72
[T]here will always be spies, and spooks, and counterspooks. Some of these slimeballs are perhaps breaking into Pentagon computers at this very moment, finding the dirty pictures some bored programmer stored on a corner of the hard disk.
1995, Dinty W. Moore, “Back to Nature”, in The Emperor’s Virtual Clothes: The Naked Truth about Internet Culture, Chapel Hill, N.C.: Algonquin Books of Chapel Hill, Workman Publishing, page 199
Meanwhile, the film's villain, played by Ben Mendelsohn, is a bigwig slimeball who wants to monopolize and monetize The Oasis through excessive pop-up ads. His true crime, though, is that he's a total noob who doesn't know his stuff.
2018 March 26, A. A. Dowd, “Steven Spielberg Finds Fun, and maybe even a Soul, in the Pandering Pastiche of Ready Player One”, in The A.V. Club, archived from the original on 31 May 2018