Definition of "illegitimate"

[…] it may be impossible to convince them that the illegitimate power which they obtain, by degrading themselves, is a curse […]

1791 (date written), Mary Wollstonecraft, chapter 2, in A Vindication of the Rights of Woman: With Strictures on Political and Moral Subjects, 1st American edition, Boston, Mass.: […] Peter Edes for Thomas and Andrews, […], published 1792

The so-called interstellar space […] has not the properties of ordinary space. It will not conduct sound, nor can a human being move through it. It is therefore illegitimate to measure it in miles.

1927, J. B. S. Haldane, “Possible Worlds”, in Possible Worlds and Other Essays‎, London: Chatto and Windus

Our attitude was that, to put it briefly, our presence there [in South Africa] was legal but illegitimate. We had an abstract right to be there, a birthright, but the basis of that right was fraudulent. Our presence was grounded in a crime, namely colonial conquest, perpetuated by apartheid.

2009, J. M. Coetzee, “Martin”, in Summertime‎, New York: Viking, page 209

[…] if things went on at this rate it would be doubtful soon whether ever again he would be able to win another election by methods legitimate or illegitimate.

1914, Theodore Dreiser, chapter 54, in The Titan‎, New York: John Lane, page 475

If we credit the scandal of the former [i.e. his enemies], Artaxerxes sprang from the illegitimate commerce of a tanner’s wife with a common soldier.

1783, Edward Gibbon, chapter 8, in The History of the Decline and Fall of the Roman Empire‎, volume 1, London: W. Strahan and T. Cadell, page 317

His illegitimate birth deprived him of the influence of a father until perhaps his fifth year […]

1916, chapter 6, in Abraham Brill, transl., Leonardo da Vinci: A Psychosexual Study of an Infantile Reminiscence‎, New York: Moffat, Yard, page 118

[…] in natural things we must have recourse […] to experience. And all reasoning that is not supported so, ought to be repudiated, or at least suspected to be illegitimate.

1658, Kenelm Digby, A Late Discourse […] Touching the Cure of Wounds by the Powder of Sympathy‎, London: R. Lownes and T. Davies, page 75

[…] it is illegitimate to reduce an Equation, by subducting from one Side a Quantity when it is not to be destroyed, or when an equal Quantity is not subducted from the other Side of the Equation:

1734, George Berkeley, The Analyst‎, London: J. Tonson, Section 27, pp. 44-45

[…] the legitimate unions between the two forms of the above nine species of Primula are much more fertile than the illegitimate unions; although in the latter case pollen was always taken from a distinct plant of the same form.

1877, Charles Darwin, chapter 1, in The Different Forms of Flowers on Plants of the Same Species‎

Her father and mine was a shameless man and of all his illegitimates I am the most unfortunate and poverty stricken.

1966, Jean Rhys, Wide Sargasso Sea‎, New York: Norton, Part 2, p. 96