Green’s Dictionary of Slang

pill v.

[pill n. (1e)]

1. in senses of rejecting or failing someone.

(a) to blackball.

[UK]G.J. Whyte-Melville Digby Grand (1890) 264: The three hateful black-balls, which constitute a rejction, announced that ‘Grand was pilled.’.
[UK]G.A. Sala Quite Alone I 32: Got nothing but black balls [...] his proposer stayed away, and his seconder came from Scotland on purpose to pill him. There was one white ball, but that was from a fellow who was short-sighted, and popped his pill into the wrong side.
[UK]Sl. Dict.
[UK]Cornhill Mag. Oct. 412: [Heading] On being ‘Pilled’ There may be some folks who don't know — / do — what it is to be ‘pilled’.
[UK]G.A. Sala Things I Have Seen I 34: There are [...] a whole bushel of reasons, most of them unlooked-for, why a man gets ‘pilled’ at a London club.
[UK]D. Cotsford Society Snapshots 308: Bobbie (across the table to Bertie). You know your friend Contango has been pilled at the ‘Marmosets’? [...] Bertie. Howling cad . . . I can’t help his not getting in.
[UK]A. Lunn Harrovians 112: An Englishman can’t enjoy anything, not even his tea, unless he thinks that he can pill his friend and stop him having tea in the same place.

(b) to fail a candidate in an examination.

[UK]A.S.M. Hutchinson Once aboard the Lugger I i 15: ‘Your examination?’ George half turned away. The bitterest moment of a sad day had come. He growled: ‘Pipped.’ ‘Pipped?’ ‘Pilled.’ ‘Pilled?’ ‘Spun... I failed. I was referred for three months.’ .
[UK]W. Deeping Sorrell and Son 208: Gorringe had a sick face [...] ‘Pilled,’ thought Kit, and was not sorry, for Gorringe needed a course of pilling.

2. (Aus.) to shoot dead .

[NZ]Eve. Post (Wellington) 9 Apr. 1: He was getting so daring that we decided to pill him first pop.
[Aus]Bulletin (Sydney) 21 Nov. 15: Not lost, but gone before. / Amateur Sport (after some hours unsuccessful shooting): ‘What has become of the – aw – dog?’ / Weary Keeper: ‘The dawg? Oh, yer pilled him two hours ago.’.

In phrases

pill up (v.) [pill n. (3b); image is of ostentation, showiness]

(US campus) to get dressed up.

[US]L.H. Bagg Four Years at Yale 46: Pill [...] Recently the word has been used as a verb, in the sense of dress, and to pill up signifies to put on one’s good clothes, to fix up, to rig out.