See subject. Vulgar as in used commonly, like “blowjob.” Not a contrived one, like, I don’t know, a “rug-munch.”
I took a look at the Wikipedia page on it, and it says at the top: “`Eating pussy’ redirects here.”
I edited the title to say “there” rather than “the,” assuming that’s what you meant?
Going down would be the most common I guess.
Those aren’t nouns.
Dining at the Y.
Mustache ride
Oh, the OP was asking specifically for nouns?
I think the common term in Japanese is kunni, which is just short for cunnilingus. It’s a noun.
Yes, thanks. And thanks for taking care of my misposting.
Scarf.
And “Box Lunch at the Y”
That’s not even a back-form of “scarfing” in English.
So far, none of suggestions are common nouns. Even the made-up ones, which would sound even more contrived with an adjective, which go fine with “blowjob.” Great, incredible, long, most scumptilicious (not really), etc. etc.
Is the Japanese one used commonly in the way “blowjob” is?
Or just Box Lunch.
I’ve heard taste, as in “may have a taste?”
It seems to me that by your own standard, “blowjob” wouldn’t count either, since it’s a compound word.
To play pop-psychologist, I think the fundamental, cultural difference between the two explains why one is considered more vulgar than the other. Namely a blowjob is often considered an act of power and domination that a guy almost always wants from any woman totally regardless of how he feels about her or she feels about him, whether it’s pleasurable or humiliating or merely a chore. A man going down on a woman is almost universally viewed as completely the opposite, something positive & caring and wanted & enjoyed equally by both partners.
In other words, cause us men are pigs! 
In Greek there is “Γλειφομούνι” (gleifomoúni / ghlee-foh-MOON-ee), literally: “lickcunt”.