Sometimes an error is so brilliant that I can’t for a moment imagine what the intended word was. This is one of those times.
I don’t remember if the sentence was referring to someone who was mouldering in the grave or someone who was merely falling apart.
Having taken a moment, I know that what my student meant was “disintegrating”: breaking or decomposing into constituent elements, parts, or particles. This happens to many things in many ways, but one thing is a corpse and one way is by means of decomposition. A personality can also disintegrate, if a person falls into a dissociative kind of madness.
The expression “disintegrating away” is nonstandard but certainly emphasizes the completeness of the process. Break something up into small enough constituent elements and eventually it isn’t there at all.
But where decentigrading came in….
It isn’t recognized as a legitimate English word, so I don’t think we can blame Spell-check here. If I type “decentig” into a Word document and run Spell-check, the suggestions are “decanter” and “dissenter” and variations thereof. That’s pretty imaginative of the artificial intelligence making the guess, but nowhere near the choice my student made. “Decenti” yields “decent,” “descent,” and “docent.” “Decentigrade” produces only “decent grade,” which is surely in my student’s fantasies but not appropriate for the sentence. “Decentigrading” is entirely the work of my student.
“Disintegrate” became “decentigrade” in my writer’s ear canal. Yes, aloud the words are similar, and someone who hasn’t seen them both may likely write one instead of the other, “sounding out” the spelling as she may have been taught long ago. The supportive teacher doesn’t fall apart laughing: she deploys the red pen to make the necessary correction, perhaps noting “WW”—”wrong word”—in the margin.
The all-too-human reader, though, collapses over the paper in helpless laughter.
I have seen many a crime show on television, with the coroner deploying that thermometer to ascertain the Time of Death by seeing how far the corpse’s body temperature has fallen. On American television, though, and in American crime novels, the coroner is measuring a decline from 98.6° Fahrenheit, not Centigrade (i.e., Celsius, which measures on a scale of 100). The murderee would then be defahrenheiting away, presumably. Decentigrading would happen elsewhere in the world, in one of those metric countries.
Maybe “decentigrading away” would describe a country that decided to change back from metric to Fahrenheit?
Could my student have been picturing a thermometer at the scene of a crime, the mercury dropping through degree after degree? Oh, I do hope so. I would rather think I have a student drawing on a field of reference full of vivid pictures of events, than a student who writes a word the way it sounds without giving a moment’s thought to what the spelling suggests.
“What’s the state of the body?” asks the scene-of-crime officer. “Ah, I’m afraid he’s decentigrading away at a pretty fast rate,” replies the coroner. Decomposition, disintegration, has begun but will only be completed a long time from now; but the decentigration will be quickly accomplished, especially if the murder occurred in a northern country during the winter and the body has lain out all night.