This is a list of Lovecraftian words I found and used when writing my MLP:FiM/Lovecraft fic At the Mountains of Discord.
Aberrant, Abominable, Absurd, Abysmal, Acidic, Acrocephalic, Adhesive, Adipose, Airy, Alien, Ambiguous, Amoebic, Amorphous, Anarchic, Ancient, Angular, Animalistic, Animated, Anomalous, Antediluvian, Anthropophagous, Appalling, Appendaged, Aquatic, Ashen, Askew, Astounding, Atrocious, Awry, Baboon-Like, Baleful, Baneful, Bankrupt, Barbarous, Batrachian, Beastly, Bellowing, Bestial, Bilious, Bizarre, Blasphemous, Bleating, Bloated, Bloodshot, Blubbery, Boiling, Bombilating, Brutish, Bug-Eyed, Bulbous, Cacaphonous, Cackling, Cadaverous, Cancerous, Cellular, Changeable, Chaotic, Chattering, Chelonian, Chitinous, Chthonic, Clawed, Coarse, Colorless, Colossal, Confusing, Congealed, Conical, Convoluted, Corpse-Like, Corpulent, Corrupt, Creamy, Criminal, Croaking, Crustaceous, Crystalline, Cunning, Cyclopean, Cylindrical, Dank, Dark, Dazzling, Deafening, Deathless, Debased, Debauched, Decomposing, Deformed, Degenerate, Degraded, Delirious, Demonic, Depraved, Deranged, Detestable, Deviant, Devilish, Diabolical, Diffuse, Dire, Discordant, Diseased, Disfigured, Disgusting, Dislocated, Disordered, Dissolved, Distorted, Dreadful, Dripping, Effervescent, Effulgent, Effusive, Elastic, Elephantine, Elongated, Emaciated, Endless, Enlarged, Enormous, Enveloping, Evasive, Exaggerated, Excruciating, Extended, Fabulous, Faceless, Fantastic, Fearful, Fecund, Festering, Fetid, Fibrous, Fiendish, Fiery, Filthy, Fish-Like, Flabby, Flailing, Flatulent, Flowing, Fluctuating, Fluid, Foaming, Foul, Fractured, Fragrant, Frantic, Fungous, Furfuraceous, Furious, Gangrenous, Gargantuan, Gaunt, Ghastly, Ghoulish, Gibbering, Gigantic, Globular, Glutinous, Gluttonous, Gnashing, Gory, Grasping, Grayish, Greenish, Grim, Grisly, Gross, Grotesque, Gushing, Hairy, Hallucinatory, Hapless, Hateful, Hazy, Heaving, Hellish, Herpetiform, Hideous, Hircine, Hissing, Horned, Horrible, Horrific, Horrifying, Howling, Huge, Hump-Backed, Hybrid, Ichorous, Idiotic, Illogical, Immaterial, Immense, Immoral, Incestous, Incoherent, Incomplete, Incongruous, Incredible, Indistinct, Infected, Infernal, Infested, Inhuman, Insane, Insatiable, Insidious, Insipid, Invidious, Iridescent, Irrational, Irregular, Jabbering, Jaded, Jangling, Jaundiced, Jellified, Jumbled, Jutting, Kleptomaniacal, Leprous, Limp, Liquefied, Loathsome, Lumbering, Luminescent, Lumpy, Lunatic, Lurking, Mad, Maggoty, Malevolent, Malformed, Malicious, Malignant, Mangy, Massive, Melancholic, Membranous, Menacing, Mesmerizing, Metallic, Mildewed, Mindless, Miscarried, Misshapen, Moaning, Molten, Molting, Monstrous, Monumental, Morbid, Mordant, Morose, Mortifying, Mottled, Mouldering, Mucky, Mucous, Murderous, Murmuring, Mutilated, Nagging, Nameless, Nauseous, Nearsighted, Nebulous, Necromantic, Necrotic, Nictating, Nightmarish, Noiseless, Non-Euclidian, Nonsensical, Noxious, Numbing, Obese, Obscene, Obsequious, Octopoid, Odious, Odorous, Oily, Oleaginous, Ominous, Oozing, Organic, Otiose, Outlandish, Oval, Overgrown, Overripe, Pagan, Pale, Pallid, Palpitating, Palsied, Parasitic, Pasty, Peculiar, Pendulous, Perfidious, Perverse, Pestilent, Phlegmatic, Pitiless, Plastic, Pliable, Poisonous, Porous, Pregnant, Prodigious, Profane, Profuse, Prognathous, Pronged, Protoplasmic, Protuberant, Prurient, Pseudopoidal, Puckered, Pudding-Like, Pulsating, Pulsing, Pustular, Pustulent, Putrid, Pyriform, Quavering, Queasy, Quiescent, Quivering, Radiant, Rainbowed, Recrudescent, Rectangular, Reeking, Refulgent, Remorseless, Repellent, Reprehensible, Reptilian, Repugnant, Repulsive, Resplendent, Restless, Rheumy, Rigid, Roiling, Rotten, Rotting, Rough, Rubbery, Rugose, Sacrilegious, Sallow, Sanguine, Satanic, Scabby, Scabrous, Scaly, Scintillating, Screaming, Scrofulous, Scummy, Sebaceous, Seething, Segmented, Senescent, Senseless, Sepulchral, Shadowy, Shiny, Shivering, Shrieking, Shuffling, Sickly, Sightless, Simian, Sinewy, Singular, Skeletal, Sleepless, Slimy, Slippery, Slithering, Slobbering, Sluggish, Solemn, Sordid, Soundless, Spectral, Spherical, Spiky, Sponge-Like, Squamous, Stagnant, Stentorian, Sticky, Stupefying, Stupendous, Stygian, Sulphurous, Syrupy, Teeming, Tentacled, Terrible, Thickening, Thrashing, Throbbing, Toothy, Transformed, Transparent, Tubular, Tumultuous, Turbid, Turbulent, Ugly, Ultimate, Umber, Unclean, Uncouth, Undigested, Ungainly, Unhallowed, Unholy, Unknown, Unmasked, Unnatural, Unripe, Unseen, Unspeakable, Unutterable, Vague, Vaporous, Vast, Venous, Vermillion, Verminous, Vestigial, Vibrating, Vile, Viperous, Viscous, Vivid, Voluminous, Vomiting, Voracious, Vulpine, Wailing, Wan, Warped, Waxen, Webbed, Wet, Whirling, Whithered, Worm-Eaten, Wormy, Wretched, Writhing, Xanthous, Xenophobic, Yammering, Yonic, Zodiacal, Zymotic