Green’s Dictionary of Slang

very, extremely.

[1826		Pierce Egan’s Life in London 12 Mar. 470/2: [A] tall sturdy subject, in a well-made, but mach torn and very muddy suit of black, and without either shoes or stockings, was charged with having been ‘mad drunk’].
[1878		Yorks. Post 4 Oct. 4/3: He found the constable [...] lying across a beer barrel, mad drunk].
1942		J. Lees-Milne Ancestral Voices diary 31 Dec. (1975) 138: I feel sure Benton Fletcher, who is mad keen for us to buy the house, and who quite likes me, will forgive me.
1996		P. Howard The Joy (2015) [ebook] I was mad into her.
2000		Hip-Hop Connection Jan./Feb. 55: ‘Mad skillz’ means a lot of skills, ‘she’s mad fly’ means a girl is very fly.
2011		G. Hayward Corruption Officer [ebook] Ch. 32: The job itself, for me, is mad easy [...] just like hanging on the block.
2012		N.Y. Times 18 Jan. 🌐 I will say something like ‘Oh that was mad good,’ or ‘Oh you think your [sic] mad cute’.
2017		Harlem Spartans ‘Kennington Where It Started’ 🎵 That’s all mad depressing.
2020		G. Armstrong Young Team 48: Addison is lookin mad para.
2021		P Howard Braywatch 205: ‘He finds it mad hard to understand you’.
2023		Rayman & Blau Riker’s 398: I was up mad late.