I’ll explain what it’s all about soon enough. I’ll leave it to run a while longer, though.
It isn’t pornographic.
If I treat it as word-association, three things come to mind in rapid succession. [spoiler]Of the sky. (What it actually means. Yes, this could mean outer space, but it could also mean the illusion of a blue dome overhead.)
Teh upper heaven in Mormon eschatology. (Thanks, LDS bestie!)
The “Unknowable Celestials” in Kirby’s Marvel work. (Space Gods. Really big.)
Mostly, “of the sky.”[/spoiler]
Ok, I’ll play too.
Having to do with the sky, or with heaven. Oh, and I guess there’s that brand of herbal teas with that name, too… Celestial Teas or something?
I can’t figure out what other meanings other people might get out of it.
heavenly
Of the heavens. Ethereal.
heavenly; astronomically-related
space, stars, then tea.
Not pornographic, huh? Okay, no idea, then.
Unless you were thinking of its specialized sense to mean:
In some outlaw Mormon branch or other, isn’t the phrase “celestial marriage” used as a poor excuse/euphemism for an older man to have multiple underage sexual partners?
Heavenly: to do with the sky (especially astronomical bodies) or the gods (who traditionally live in the sky; (by metaphorical extension) wonderful and beautiful.
That is out of my head, and without looking at other people’s answers.
What do I win?
“Of the sky,” usually in scientific context (i.e., Celestial Object.) I’d be hard pressed to think of any other different use I would have for the word
See below…
starry
heavenly
sacred/otherworldly in some contexts, as in the phrase celestial host
Also brought to mind: the musical instrument the celeste, and Babar the Elephant’s wife, but those can’t be what you have in mind, surely.
And I probably should have said metonymic extension, rather than metaphorical, huh?
Pertaining to the cosmos/stars/outer space.
I decided to read this far before posting, and since all the “first thing to pop into my mind” meanings and synonyms that I would have mentioned have been mentioned multiple times I’ll just add a few oddball things in my memory:
[spoiler] -Brother Dave Gardner, a stand-up comedian from my college years, used to say “Ain’t that celestial?” as a tagline to something far out or absurd.
-Aren’t there some Celestial Seasonings brand spices or condiments?
-The thing about the Chinese did sound a little familiar but I can’t attribute it to a specific source or time I might have heard it
[/spoiler]
Do be a nice person and tell us your theory or whatever. Don’t allow this to become another
or worse. 
I’m guessing he’s referring to the meaning Senegoid references.
(Which I have heard of and would only stumble over briefly if I ran into it in its native context, but is not, due to its complete archaicness and from what I’ve seen, rarity even in that context, would never in a million years think of unbidden.)
Possibly, but there are other possibilities, including the one I mentioned:
The Mormon-offshoot illegal “celestial marriage”.
I’m sure the OP will be back soon to clue us in. He’s been around the SDMB a while.
[spoiler]Of or having to do with the stars in the sky.
Also a type of creature built using the template of the same name, conveying resistances, strength, magic resistance, and the Outsider designation.[/spoiler]
Interesting revelation as to how many of us have been proudly posting for years, without ever reading the full OP.
pertaining to the sky, heaven, or outer space
So only synonyms?
Heavenly
Divine
Stellar