tamper

Etymology 1

tamp + -er

noun

1. A person or thing that tamps.
2. A tool used to tamp something down, such as tobacco in a pipe.
3. (rail transport) A railway vehicle used to tamp down ballast.
4. An envelope of neutron-reflecting material in a nuclear weapon, used to delay the expansion of the reacting material and thus produce a longer-lasting and more energetic explosion.

Etymology 2

From Middle French temprer (“to temper, mix, meddle”). Doublet of temper.

verb

1. (intransitive) To make unauthorized or improper alterations, sometimes causing deliberate damage; to meddle (with something).
   tamper detection
   The alarm had been tampered with and didn’t go off when it should have.
   The election monitors found that a large number of ballots had been tampered with.
   Our body is as a well-set clock which keeps good time; if it be too much or indiscreetly tamper’d with, the larum runs out before the houre. 1640, Joseph Hall, Christian Moderation, London: Nathaniel Butter, Book 1, § 7, p. 70
   […] of those Books that passe for authentick who knows what hath bin tamper’d withall, what hath bin raz’d out, what hath bin inserted […] 1641, John Milton, Of Reformation, Thomas Underhill, page 25
   These extraordinary capacities of life have been ignored by the practitioners of chemical control who have brought to their task […] no humility before the vast forces with which they tamper. 1962, Rachel Carson, chapter 17, in Silent Spring, Boston: Houghton Mifflin, page 297
2. (intransitive) To try to influence someone, usually in an illegal or devious way; to try to deal (with someone).
   Prosecutors argued that he would tamper with witnesses if bail was granted.
   […] no man knowes whether a Wife and a Mother, which had such a latitude of power over the Father and the Sonne, would not be tampering with a Prince (even in the point of Religion) of so tender years as rendred him fit for any impression, and to be indoctrinated with such principles as well concerning Religion, as others best suitable to her own designes. 1651, John Milton, The Life and Reigne of King Charls, London: W. Reybold, page 217
   […] as these passions and principles are inalterable, it may be thought, that our conduct, which depends on them, must be so too, and that ’twou’d be in vain, either for moralists or politicians, to tamper with us, or attempt to change the usual course of our actions, with a view to public interest. 1740, David Hume, A Treatise of Human Nature, London: John Noon, Volume 3, Part 2, Section 5, p. 110
   The Maroons […] had not been tampered with by the French, nor had they themselves, at this time, tampered with the slaves. 1803, Robert Charles Dallas, The History of the Maroons, London: Longman and Rees, Volume 1, Letter 6, p. 169
3. (dated) To meddle (with something) in order to corrupt or pervert it.
   1741, Samuel Richardson, Pamela, London: C. Rivington and J. Osborn, Volume 1, “To my worthy Friend, the Editor of PAMELA,” p. xii, […] No Art used to inflame him, no Coquetry practised to tempt or intice him, and no Prudery or Affectation to tamper with his Passions; but, on the contrary, artless and unpractised in the Wiles of the World, all her Endeavours, and even all her Wishes, tended only to render herself as un-amiable as she could in his Eyes:
   She therefore dissuaded Julia from attempting to tamper with the honesty of a servant who had the keys of the vaults […] 1790, Ann Radcliffe, chapter 11, in A Sicilian Romance, volume 2, London: T. Hookham, page 77
   Is it not the tendency, born of Reconstruction and Reaction, to found a society on lawlessness and deception, to tamper with the moral fibre of a naturally honest and straightforward people until the whites threaten to become ungovernable tyrants and the blacks criminals and hypocrites? 1903, W. E. B. Du Bois, chapter 10, in The Souls of Black Folk, Chicago: A. C. McClurg, page 204
4. (obsolete) To involve oneself (in a plot, scheme, etc.).
   1716, Joseph Addison, The Free-holder, No. 31, 6 April, 1716, London: D. Midwinter and J. Tonson, p. 180, […] he was beheaded upon the Defeat of the Conspiracy for having but thus far tampered in it.
5. (obsolete) To attempt to practise or administer something (especially medicine) without sufficient knowledge or qualifications.
   Certainly it is a scurvy strong troublesom purge, therefore ill to be tamperd with by the unskilful […] 1649, Nicholas Culpeper, transl., A Physicall Director, London: Peter Cole, page 29
   […] by reason of his continual studies, and the head-ach, to which he was subject from his youth, and his perpetual tampering with physic, his eyes had been decaying for twelve years before. 1753, Robert Shiells, “John Milton”, in The Lives of the Poets of Great Britain and Ireland, volume 2, London: R. Griffiths, pages 120–121
6. (US, Canada, in professional sports) To discuss future contracts with a player, against league rules.