What does "Oh snap!" mean?

That is right. And since, as you said it’s so close to the “quarter to/til” construction, I was startled that it was something people had to think about. OTOH, I’ve heard quarter of since before I could tell time and it was reinforced by being the default way to speak about time in school, so I guess that’s an advantage over people just hearing it for the first time.

Here’s a confused peron elsewhere It's A Quarter Of Six?

That’s the Z Snap. Compare:

The Z Snap
Oh Snap!

That so many of you haven’t heard of this is funny to me. It wasn’t even all that popular in my school (though it did get some use) because it’s so played out that anyone saying it would almost certainly be doing it ironically. It wasn’t ever explained to me, it’s just obvious from context what it means.

I had never heard of it until a few years ago when my kids were watching “That’s So Raven,” in which they seemed to say it at least once per episode. In that show, it was obviously a substitute for something like, “Oh, shit.”

That’s correct. That’s the only way I’ve ever heard it used, as in the card game, meaning “me too”.

If the game Snap isn’t played in the US, or is called something different to “Snap”, there’s your answer; people heard it and didn’t grasp the card game context and started using it in some other way. But if anyone said “Oh snap” to me I’d think they were saying “Oh, me too” because until opening this thread I’ve never heard it used any other way.

ETA: I’m 46, that usage dates back at least to my childhood in the 1970s

I concur with all of this - few things have surprised me more on the SDMB than it taking until the bottom of the first page before someone mentioned the card game.

Ha ha ha! I thought you were being sarcastic. I always thought ‘oh snap’ acknowledged a zinger that was really a zinger but was all wit and not really insulting in itself- like the speaker remains beyond reproach in his speech even though he is putting someone else down. Because Dawkins is being insulting and over-reaching, I thought you didn’t really mean it.

So maybe nobody ever understands anybody on these boards, which would explain a lot.

That’s where I’ve seen it! Except Chrome says “Aw, Snap!”, and it definitely means it in the, “Oh s***, something’s gone wrong!” sense.

There’s a screengrab right at the bottom of this blog which discusses “Oh snap”.

I’m an old guy who has lived in seven different states; I’ve never in my life actually heard anyone use the phrase “Oh, snap.” The only place I’ve seen it written out is right here on the SDMB. I don’t watch TV very much.