Green’s Dictionary of Slang

big spit n.

(Aus.) the act of vomiting; also as v.

1959		R.A.N. News (Sydney) 20 Mar. 4: Down in the Strait / The waves rolled high / The waves rolled wide / And the ‘Big Spit’ starters lined the side [AND].
1967		F.J. Hardy in Great Aus. Lover Stories 63: Euphemisms for vomit [...] include spue, burp, hurl, the big spit, the long spit.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 21: Big Spit Vomit.
1988		McGill Dict. of Kiwi Sl. 14/2: big spit, the vomit.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
2010		J. Miller Lingo Dict. 16: big spit; to vomit.

In phrases

go (for) the big spit (v.)

(Aus.) to vomit.

1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 67: You can keep the cider, thanks [...] It always makes me go the big spit.
1964		I. Fleming You Only Live Twice 46: Soon as we got home from that lousy cat house, I had to go for the big spit.
1969		A. Buzo Rooted I iii: Remember the time he got sick at Davo’s twenty-first and went for the big spit? He said to me ‘Jees I feel crook’, and then he [...] shoved his head out the window and burped a rainbow.
1985		B. Humphries Traveller’s Tool 119: This is a reference to witchetty grubs which, like all ethnic delicacies, would more than likely have you and me going for the big spit and yodelling into the white telephone.
1988		McGill Dict. of Kiwi Sl. 14/2: big spit, the vomit, often in phr. ‘to go for the big spit’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].