Green’s Dictionary of Slang

1. a debauchee, a degenerate; in weak use, one who lives for pleasure.

1873		Once a Week 8 Mar. 205/1: He’s a hot member as I’ve laid it [i.e. a bet] to. These swells don’t come outside unless they know something.
1880		E.J. Milliken ‘Cad’s Calendar’ in Punch Almanack n.p.: If a chap’s a genuine hot member, / He can keep the game up in November!
1896		Ade Artie (1963) 9: Oh, but they was hot members!

2. one who flouts convention.

1902

Ade Forty Modern Fables 237: The Man who could sport a Velvet Vest and a pair of Blue-Topped Boots was considered a Hot Member.

3. a troublesome, bad-tempered, quarrelsome person.

1880		Bulletin (Sydney) 31 Jan. 3/2: [T]he amphibious devil-dodger and soul-saver commenced by saying that he was a ‘hot member,’ who could be very rough on the profane, and that, however much it might look like one, the ceremony was not a pantomime, but a very solemn and blessed affair indeed.
1880		New Babylon 24 July 5/2: [of a horse] [A] Hot Member he was, but he had got a hotter in the saddle. ‘The Demon,’ [...] tried his level best, to unseat her, but it was of no use.
1901		‘Miles Franklin’ My Brilliant Career 163: He gets mad if anyone dares to monopolise you [...] He is a pretty hot member sometimes.
1907		E. Dyson ‘Two Battlers and a Bear’ in Lone Hand (Sydney) Oct. 604/1: ‘Well, you’re a ’ot member [...] er fair take-down’.
1909		J. Ware Passing Eng. of the Victorian Era 155/1: Hot member (Peoples’, 1880–82). A troublesome, quarrelsome man. The phrase was rarely applied to a woman, probably because it appears to have taken its rise about the time when the Irish obstructionists in the Commons drew general attention to the vigour of the Nationalists-as they afterwards came to be called.

4. (US) the penis [member n.¹ ].

1916

H.N. Cary Sl. of Venery.

5. (US) a sexually attractive woman, also a prostitute.

1897		Ade Pink Marsh (1963) 133: Little ol’ Miss Lo’ena’s hot membeh. She’s so wahm you can feel ’e heat on otheh side of ’e street when she goes past.
1949		Monteleone Criminal Sl. (rev. edn).