Never heard slash for vomitting before, to vomit is usually hurl or simply throw up.
Only time I’ve heard of slash for a bodily function was in a dictionary that defined fart as a slashing noise between the legs. (Another dictionary substituted grinding in place of slashing).
Never heard of it used in the context of any bodily function.
I learned ‘slash’ as slang for urinating when I watched Braindead. Never heard it for vomiting.
I’m surprised no one has mentioned ‘spew’ yet. That’s the one I use.
‘Oh, man! I was so drunk I blew chunks!’
‘It’s all right. We all drink until we spew once in a while.’
‘You don’t understand. Chunks is my dog.’
One good thing I’m getting from this thread is that if I needed a “password” to confirm the validity of somebody claiming to be from Central Alabama from the years 1954-1959, all I’d have to do is use the word “slash” in a context that might be taken as referring to either of the bodily functions under discussion and if the person claimed to be from that area and thought it was referring to urination, I’d know he/she was an impostor.
Maybe there are similar words that have regional identity for your area that could be used by you for a similar purpose of catching an impostor.
Taking a slash in Aus-speak definitely refers to urinating, esp of a male. Women tend to use more delicate language, like “I’m heading off to the dunny to take a piss, who’s coming with me?” 
Apart from all the other variants of vomit, there’s also chunder. *Apparently *derives from old seafaring times, when those on the upper-deck, overcome with an urgent biliousness, would warn those on the lower decks that they were about to hurl.
Chunder = **WATCH UNDER. **
Ah, yes, as popularized in the lyrics of “Down Under” by Men At Work. Never knew it came from “watch under.”
Someone at the Norman Lindsay Gallery assures me of the truth of this origin.
from Australian National Dictionary Centre
Apparently the first written reference was in Neville Shute’s 1950 novel * A Town Like Alice*, so both origins seem dubious.
Same here. I grew up in north central Alabama and have lived in west central Alabama for over 20 years and I’ve never heard this.
That’s so odd to me that, if you said it in a regular conversation, I wouldn’t even be able to figure it out through context what you were on about.