Green’s Dictionary of Slang

1. very fond of; determined (to do something).

1862		Worcs. Chron. 12 Nov. 4/1: The coppers were dead on sneaking for it.
1871		London Figaro 13 May 3, col. 2: Bill’s dead on for a lark with the canting bloke [...] [F&H].
1888–94		‘Walter’ My Secret Life (1966) IV 738: Her mind was dead on rogering.
1894		Fort Worth Gaz. (TX) 1 July 5/6: I’m dead on Mr Paul [...] He has de long green t’ burn a wet dog.

2. (orig. US) dealing very strictly and severely with a situation or person.

1878		‘’Arry on Himself’ in Punch 21 Dec. in P. Marks (2006) 6: I’m dead on the high lardy-dardy, I loathes a straight-lacer or saint.
1883		Nat. Police Gaz. (NY) 10 Nov. 6/2: ‘Are you such a gilly [...] that when you were dead on to him, you didn’t pull the rocks’.
1897		E.W. Townsend Chimmie Fadden 4: Say, I could have give him a string bout me being a hard-working boy, but I knowed de lady was dead on t’ me.
1904		N.Y. Times 31 Jan. 27/6–7: But if after some time Mr. Smith begins to ‘rubberneck,’ [to] dart in through one of these and out through another, then the latter will know by these symptoms that Mr. Smith is beginning to feel annoyed, that is, he is ‘getting tired of his face,’ or ‘dead on,’ in detective parlance.
1915		Edinburgh Eve. News 1 May 7/5: Eager to Get ‘Dead On’ ‘Let’s swipe the Germans off the face of the earth’.

3. (orig. US) absolutely right, utterly correct, exact [modern use is SE; abbr. SE dead on target].

1897		E.W. Townsend Chimmie Fadden 3: ‘Is dis Chimmie Fadden?’ says he. ‘You’re dead on,’ says I.
1946		R. Grinstead They Dug a Hole 89: Where’s Ginger? [...] He hasn’t gone after parts for that old Jerry truck, missing a dead-on fatigue like this?
1979		J. Morrow Confessions of Proinsias O’Toole 134: Dead-on, Duncher – no trouble.
1986		Beano Comic Library No. 96 63: It’s dead on tea-time!
1999		Observer 7 Nov. 3: It has opened to rave reviews. The LA Times called it a ‘dead-on tale of corporate power, courage, cowardice and how we live’.
2000		J. Hawes Dead Long Enough 244: Dead on so!
2009		L. McIlvanney All the Colours 163: I fumbled in my pocket for a fiver. ‘Here’s a donation.’ ‘Dead on’.
2012		(con. 1954) ‘Jack Tunney’ Tomato Can Comeback [ebook] The advice was dead-on.