Catamites, in ancient Greece, were the passive third gender partners, usually younger, that some men kept. It has the same connotations as a Berdache or a Ladyboy in other cultures.
Although, when seen from the western concept of 'homosexuality' which doesn't recognize 'gender orientation' or 'third gender, catamite appears to be just the younger boy in a pederastic relationship between a man and a boy, without any gender connotations. However, the ancients and the contemporary non-western cultures make a strict distinction between 'men' and 'third genders' (non-men males; males with a female orientation).
That a non-effeminate boy in a relationship with an older man, will not be called 'Catamite,' is clear from the fact that pedarasty was a normal, acceptable and honorable part of Greek culture that most boys took part in -- and it was customary for the boys to assume the passive role. However, Catamite is an extremely negative, derogatory and even abusive term, which has exactly the same connotation as the terms related with 'third gender,' in most other cultures, past or present. It is also very similar to the stigma against 'homosexual' found in modern West, which often has connotations of being 'not man enough' or being 'sissy.' It is also clear that as against what is being sought to portray about Catamites in certain sections of the gay community, Catamites did not exactly refer to 'boys' in relationships with men -- since even adult effeminate priests have been referred to as Catamites. It is obvious, that this negative term was never used for non-effeminate, non-third gender male youths or adults, nor for other non-effeminate males (like slaves; it was unacceptable for a non-slave adult man to play the passive part) who had sexual relationships with men, even if they played the passive part.
References 1. Zuni BerdachesQuote: "The Oxford English Dictionary, for example, while providing the familiar zoological and botanical definitions, also defines hermaphrodite as "an effeminate man or virile woman, a catamite," and "a person or thing in which any two opposite attributes or qualities are combined." 2. Homosexuality, Passivity and the Catamite Priests
References in literature
- In Plato's dialogue Gorgias (at 494d) Socrates uses the term in a conversation with Callicles contrasting appetites and contentment.
- The word appears widely but not necessarily frequently in the Latin literature of antiquity, from Plautus to Ausonius. It is sometimes a synonym for puer delicatus, "delicate boy". Cicero uses the term as an insult. The word became a general term for a boy groomed for sexual purposes. Also appears in Meditations by Marcus Aurelius.
- Stephen Dedalus ponders the word in Ulysses when discussing accusations that William Shakespeare might have been a pederast.
- C. S. Lewis in his partial autobiography Surprised by Joy described the social roles during his time at Wyvern College (by which he meant Malvern College) as including the role of "Tart": "a pretty and effeminate-looking small boy who acts as a catamite to one or more of his seniors..." and noted that "pederasty...was not [frowned upon as seriously as] wearing one's coat unbuttoned." 
- Anthony Burgess's 1980 novel Earthly Powers uses the word in its "outrageously provocative" opening sentence: "It was the afternoon of my eighty-first birthday, and I was in bed with my catamite when Ali announced that the archbishop had come to see me."
- In the postapocalyptic landscape of Cormac McCarthy's novel The Road, the narrator describes an army on the move on foot with "women, perhaps a dozen in number, some of them pregnant, and lastly a supplementary consort of catamites." 
- Cicero, frg. B29 of his orations and Philippics 2.77; Bertocchi and Maraldi, "Menaechmus quidam," p. 95.
- Surprised by Joy: The Shape of My Early Life, Chapter VI Bloodery, pp.83-84, C. S. Lewis
- "An arresting opening". Telegraph. Retrieved August 30, 2012.
- McCarthy, Cormac (2006). The Road. Vintage International. p. 92. ISBN 9780307387899.
- The dictionary definition of catamite at Wiktionary