Green’s Dictionary of Slang

1. anyone or anything seen as especially important, large or powerful.

1869		‘South-Western Sl.’ in Overland Monthly (CA) Aug. 130: When two roughs fall to quarrelling about any matter, one of them usually administers to the other some species of a ‘snifter’ or ‘curries him down with a six-shooter’.
1917		Rising Sun 22 Jan. 3/2: He spun some snifters when he got going.
1918		Burra Record 27 Feb. 3/4: In true Australian slang it was acknowledged as a ‘snodger’ spree, a ‘snifter’.
1920		Advocate (Burnie, Tas.) 5 June 7/2: Snorkey, you’re a snitty bonser! Tres beans! A snifter.
1934		C. Drew ‘Zarko Assassin’ in Bulletin 23 Oct. 49/1: It was a snifter of a headlock too, but Square Head tore his melon clear.
1963		C. Mann ‘Stiff Luck for the Colonel’ in Three Stories 54: [i.e. a winning horse] You’re right! Six thousand lovely smackers! You little snifter!

2. in ext. use, an attractive woman.

1918		Aussie (France) 9 Dec. 4/1: Isn’t she a snifter? I’m butting right in! [Ibid.] 9/1: ‘Any tabbies there?’ / ‘Ah, now you’re talking! Yes, there was one in the Chateau. [...] That girl was a snifter, and no mistake!’.
1939		Argus (Melbourne) 23 Dec. 65/4: But where, oh where, did we get ‘Pratting in one’s frame’, ‘Doing one’s block,’ ‘Getting into a yike,‘ [and] ‘Snifter’.