dearorpheus:

xshayarsha:

Terrifying: forthcoming, unnerving, never seems to fully materialize, pitch-black, veiled, formless, bloodcurdling in its subtle obscure way, devouring; it teases and haunts you when you can’t even name it. It’s overall psychological – you strive to make it take shape in your mind while it feeds on suspense, indeterminacy and ignorance.

Horrifying: stark, manifest, blood-soaked in front of your very eyes, sadistic, wild, frenzied, of a shining crimson; it shocks, menaces and assails you to the point of paralysis and dementia. It’s of a more visual, physical nature and brutally unambiguous; it doesn’t depend on anything else – it’s what follows the unveiling of the terrifying.

Terror/Horror were not meant to be synonyms but to convey distinct impressions – so choose your words wisely if you want to make good old Ann Radcliffe proud! xx

I researched this for my major work!

Stephen King has three different forms of fear (as he sees them) that really capitalise on what @xshayarsha said:
1) The Gross Out: the sight of a severed head tumbling down a flight of stairs, when the lights go out and something green and slimy splatters against your arm –> irrelevant for the terror/horror discussion, but interesting nevertheless.
2) The Terror: when you come home and notice everything you own had been taken away and replaced by an exact substitute, when the lights go out and you feel something behind you, you feel it’s breath against your ear, but when you turn around there’s nothing there. As above: subtle, devouring, psychological.
3) The Horror: the unnatural, spiders the size of bears, the dead waking up and walking around, when the lights go out and something with claws grabs you by the arm. As above: manifest, menacing, visual.

Further than that, even, consider that ‘horror’ transfers similar meaning to the adjective ‘horrific’, but ‘terror’ and ‘terrific’ are seemingly opposed. 
It’s because of a semantic change called amelioration—when a word’s meaning is elevated; opposite being ‘perjoration’, which is when a word’s meaning is degraded.

The words “horror,” “horrible,” and “horrific” have their roots in the Indo-European base ghers- / ghrs- (to become stiff), according to the Chambers Dictionary of Etymology.
The terms “terror,” “terrible,” and “terrific,” Chambers tells us, are rooted in the Indo-European base ters- / tres- (to shake).
Those Indo-European roots gave Latin the verbs horrere (to bristle with fear) and terrere (to fill with fear), which inspired the Old French, Middle French, Anglo-Norman, and Modern French words that gave English such frightening language.

The meanings of all six words reflected their scary or hair-raising roots when they entered English from the 1300s to the 1600s, according to written examples in the Oxford English Dictionary:
The dictionary’s earliest citation for “terrific” in this sense is from Milton’s Paradise Lost (1667), which describes the Serpent in Paradise as a subtle beast “with brazen Eyes And hairie Main terrific.”
In less than a century, Oxford says, “terrific” took on a weakened sense: “Of great size or intensity; excessive; very severe.”
The earliest example of this new usage in the dictionary is from a 1743 translation of Horace’s lyric poetry: “How cou’d … Porphyrion of terrific size … stand against the Warrior-goddess?”
It took another century, according to the OED citations, for “terrific” to take on the modern sense of “an enthusiastic term of commendation: amazing, impressive; excellent, exceedingly good, splendid.”
The first example of this sense is from an advertisement in the Oct. 21, 1871, issue of The Athenaeum, a journal of science and the arts:
“The last lines of the first ballad are simply terrific,—something entirely different to what any English author would dream of, much less put on paper.” (x) 

It’s really interesting to approach the popular culture you consume with this knowledge, esp. the horror genre and gothic literature. 

Note: you can learn more about the theory behind it here if you’d like.