Green’s Dictionary of Slang

header n.

1. a blow to the head.

[UK]Sporting Mag. II. 279: The latter almost instantly surprised Johnson with another header.

2. going lit. or fig. ‘head-first’.

(a) in fig. use of sense 2b, a bet, usu. spontaneous and unthought-out.

[UK]J. Greenwood Unsentimental Journeys 183: He took a deliberate ‘header,’ trusting to the ‘Betting Man’s Guide’.
[UK]W.C.Russell Jack’s Courtship Ch. vii: ‘Miss Hawke,’ said I, plucking up my heart for a header and going in, so to speak, with my eyes shut and my hands clenched [F&H].

(b) a head-first dive, usu. into water.

Inside Sebastopol 297: These excellent public baths look delicious [...] we may surely shut the door and take a header.
[UK]Hotten Sl. Dict.
[Ire]C.J. Kickham Knocknagow 89: Then he cursed his stupidity for never having thought of taking a ‘header’ into a bog-hole, and remaining there with only his nose above water till they had passed.
[Aus]Bulletin (Sydney) 31 Jan. 3/3: He explained to them the utter uselessness of baptism by sprinkling, […] and clearly proved that salvation was to be attained by nothing less than a ‘header’ or a ‘dip.’.
[Aus]Bulletin (Sydney) 21 May. 4/2: This will prevent the annoyance often experienced [...] on the present bicycles, when the little wheel takes a fancy to climb up the rider’s back, and failing, leaves him to study astronomy on the sidewalk, after a ‘header’ and a few weals from the wheels.
[UK]‘Pot’ & ‘Swears’ Scarlet City 174: I have been [...] wondering when you intended to take your header through the plate glass.
[Aus]Bulletin (Sydney) 24 Feb. 11/1: The fish was dozing peacefully in about 4ft. of water when a lady bather took a header and landed on his back.
[Aus]Kia Ora Coo-ee 15 June 5/1: I went for a swim in the Dead Sea. Shut my eyes and took a header, but to my surprise, still found myself on top.
M. Meredith ‘The Human Head in Sl.’ in AS III No 5 408: To take a ‘header’ is to fall headforemost, headfirst, or headlong.
[UK]J. Curtis There Ain’t No Justice 99: ‘I took a header off of Hammersmith Bridge and drowned meself.’ ‘Yerce. You look like it.’.
[US]N. Algren Man with the Golden Arm 89: The cashier’s face white as a split apple [...] as she took a header.
[US]B. Schulberg On the Waterfront (1964) 65: I comes out the swingin’ door of McCarty’s [...] an’ do a header into a snowbank.
[US]J. Thompson Pop. 1280 in Four Novels (1983) 369: I almost took a header as I came out.
[US]San Diego Sailor 44: I [...] took a clean header through the surf.
[US]G.V. Higgins Patriot Game (1985) 72: This guy could always take a header when it really counted.
[US]J. Wambaugh Golden Orange (1991) 248: The former marine [...] staggered into the men’s room, where he took a header.
[UK]N. Cohn Yes We have No 288: Someone took a header down the stairs.
[UK]A. Sillitoe Birthday 201: I thought she was going to do a header through the windscreen.

(c) a social decline.

[US]T. Thursday ‘Mr. Mister’ in All-Story Weekly 22 May [Internet] There’s something phony about all those Mister guys. I never bumped one yet who didn’t take a header downhill sooner or later.

(d) one who jumps, usu. for the purposes of suicide, off a high building, bridge etc.

[US]S. Morgan Homeboy 207: Just spotted a header off Coit Tower.

3. (US) an act of oral copulation [head n. (2c)].

[US](con. 1951) McAleer & Dickson Unit Pride (1981) 177: ‘Want to get laid, Joe?’ she asked me. ‘How about a header instead?’ ‘O.K. Give good headers.’.
[US]N. Ross Policeman’s Bible 63: [...] a dude who was patronizing a prostitute and then forcing the broad to give him a header.
[US]J. Wambaugh Glitter Dome (1982) 218: She wasn’t interested in the hundred-dollar bag of bones who Juicy Lucy said was coming back at eight o’clock for a double header.

4. (Irish) a psychotic, an unstable or bizarre person.

[UK]L. Dunne Goodbye to The Hill (1966) 82: As I say, I was a right header.
[Ire]R. Doyle Commitments 16: Tha’ header!
[UK]C. McPherson The Weir 39: Ah she was a header. Looking for attention.
[US]K. Bruen ‘Fade To . . . Brooklyn’ in Brooklyn Noir 309: Sean is a header, a real headbanger.