illegitimate

Etymology

Based on Latin illegitimus; equivalent to il- + legitimate.

adj

1. Not conforming to known principles, or established or accepted rules or standards.
   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
2. Not in accordance with the law.
   […] 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
3. Not sanctioned by marriage.
   1. Born to unmarried parents.
      an illegitimate child
   2. (dated) Having a child or children with a person to whom one is not married.
      I heard last night that a what-do-you-call it?—claimant?—has arrived who says Pat Wayne is his illegitimate father. 1935, Carolyn Wells, chapter 13, in The Beautiful Derelict, New York: Triangle Books, page 222
4. Not correctly deduced.
   an illegitimate inference
   […] 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
5. Not authorized by good usage; not genuine.
   an illegitimate word
6. (botany) Involving the fertilization of pistils by stamens not of their own length, in heterogonously dimorphic and trimorphic flowers.
   illegitimate union; illegitimate fertilization
   […] 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

noun

1. A person born to unmarried parents.
   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

verb

1. (transitive) To make illegitimate.