Green’s Dictionary of Slang

numb adj.

1. (US, also numbs) blind drunk; occas. intoxicated by drugs.

[US] in Wisconsin Mag. of Hist. 62 240: I’m not saying that the stuff is non-intoxicating, for one can get ‘numb’ on it [HDAS].
[US]N. Algren Man with the Golden Arm 46: The customers come here to get numb off Schlitz.
[US]R. Prather Scrambled Yeggs 57: ‘What are you trying to do, woman?’ I asked her, ‘get me drunk?’ ‘No, silly. I don’t know; I just feel like getting a little stupid. Numb.’.
[US]T. Dorsey Triggerfish Twist (2002) 87: ‘How do you feel?’ asked Bernie. Coleman looked slowly around the room. ‘[...] numb, paralyzed, wired, [...].’.

2. (US, also numbass, numbfuck) stupid.

[US]Wentworth & Flexner DAS.
[US]M. Braly On the Yard (2002) 160: He’s supposed to be a schooled hustler, down with all games, so how come he lets a bunch of numb-brained fuzz catch him time after time?
[US]H.E. Roberts Third Ear n.p.: numb adj. dumb; stupid.
[US]J. Gould Maine Lingo 192: Numb—A mild version of dumb, in the sense of somewhat stupid. [...] Physical numbness, transferred to intelligence, is suggested by ‘as numb as a pounded thumb.’ A Mainer might call somebody dumb behind his back, but to his face he’d use numb: ‘You seem a little numb about learnin’ how to do that!’ .
[US]S. King Stand (1990) 1145: He threw Raphael, Donatello, and their numbfuck buddies across the store.
[US]S. King It (1987) 112: But the numb cunt he was married to was still on the phone.
[US]S. King Dreamcatcher 116: Jumping up and down now like one of those numbass bootscooters on the The Nashville Network, feeling like a jerk.

SE in slang uses

In derivatives

numby (n.) (also nummy) [abbr. numbhead ]

(US) a fool, a simpleton.

[US]J.D. Corrothers Black Cat Club 90: ‘Chop down de tree! [...] you nummies!’ yells Uncle Ephum.
J. Walsh ‘Essence, Ltd’ Fringewood News SciFi #3.10 [Internet] ‘So it does. But let me warn you, the potions that I’m selling are not toys.’ ‘I realize that. I’m not a numby or a dummy.’.

In compounds

numbhead (n.) [-head sfx (1)]

(US) a fool.

E. Burr Journal 2 Sept. in New Eng. Qly (1930) 3 314: We are about sending her to school, but Mr Burr is expecting that she will prove a numbhead .
[UK]‘C. Caustic’ Petition Against Tractorising Trumpery 90: To rattle like a roll of vellum, And occiput of every numhead To sound as loud as kettle-drum head.
[UK]Sam Sly 19 May 3/2: We advise that numhead of a fellow, R. R., Osborne-street, not to sell ha’porth’s of treacle on a Sunday afternoon.
[US]Gallipolis Jrnl (OH) 16 Dec. 1/8: Don’t you know any thing, you numb-head you?
[US]Iola Register (KS) 23 Apr. 8/5: He told the spinster that she was a gone-by old numb-head.
[US]Bourbon News (Millersburg, KY) 30 May 4/3: While the lean and scraggy ones [i.e. girls] were the choice, the numbheads were chasing after them.
[US]Burlington Wkly Free Press (VT) 4 Aug. 6/4: The silly law which the numheads in the Legislature succeeded in putting on the statute books.
[UK] in LANE.
[US] in DARE.
[US]J. Gould Maine Lingo 192: Numb—A mild version of dumb, in the sense of somewhat stupid. A numb-head doesn’t know enough to come in out of the rain.
[US]A. Pearl Dict. Popular Sl.
‘roxyrama’ Album Zone [Internet] We don’t need some numbhead who knows damn all about musical history telling us what to play, or say.
numbheaded (adj.)

(US) stupid.

[US]F.M. Whitcher Widow Bedott Papers (1863) 97–8: The old coot was so awful numbheaded I couldn’t beat anythin’ into him.
numbheadedness (n.)

(US) stupidity.

G. Schmitt Electra 293: One of those spells of numbheadedness which came upon him often of late.
numbnut (adj.) [numbnuts ]

(Aus.) foolish, stupid.

[Aus]M.B. ‘Chopper’ Read How to Shoot Friends 120: I gave Anita a pile of mail written to me by Renée to support my numbnut idea that she was a friend.
[Aus]M.B. ‘Chopper’ Read Chopper 4 43: He actually won the fight, punching ten shades of shit of the numbnut dago.
numbnuts (n.) [nuts n.2 (1)]

1. (US) an idiot, a fool; usu. as a term of address.

[US] in Current Sl. IV:3-4 (1970).
[US]M. Cherry On High Steel 92: Change the subject, numbnuts.
[US]G.V. Higgins Patriot Game (1985) 199: Yeah, numb-nuts?
[US](con. c.1970) G. Hasford Phantom Blooper 18: What is your major malfunction, numbnuts? How long will it take me to forget your name?
[US]C. Hiaasen Skinny Dip 195: Stranahan waved. ‘Over here, numbnuts!’.
[Aus]J.J. DeCeglie Drawing Dead [ebook] Watch it numb nuts . . . you almost took my fucking head off.
[Aus]T. Spicer Good Girl Stripped Bare 75: ‘The audience? Full of numbnuts. They’re the ones who reckon blondes are dummies’.

2. in attrib. use of sense 1.

[US]C. Stella Eddie’s World 201: You and that numb-nuts cousin of yours.
numbwit (adj.) [var. on dimwit ]

foolish, stupid.

[US]H.S. Thompson letter 12 Dec. in Proud Highway (1997) 34: I was thrown out of the club for calling the night manager a crude, numbwit ass.