Queer

Queer was a human epithet for homosexuality.

As a noun, "queers" could mean "deviant men". Harry Harvey, ashamed of his attraction toward David Daniels, called David "queer filth", and told him to go back to "[his] kind", that he might "infect [him]". (PROSE: Damaged Goods)

In 2009, Clement McDonald called Ianto Jones a queer, saying that he "could smell it." Ianto objected, implying through the phrase, "This isn't 1965" that the word was old-fashioned and no longer appropriate in the 21st century. (TV: Children of Earth: Day Three)

In the 21st century, Rachel Edwards, herself a bisexual, used the adjective queer, wondering how Lola Denison was with "queer stuff", to refer to issues regarding the community. (PROSE: Head of State)

Behind the scenes
Queer is a reclaimed term which functions as an umbrella for various sexual and gender minorities. For context on Ianto's comment, its use as a derogatory term was indeed at its height in the 1960s, before those in the community reappropriated the word queer in the late eighties, as a mark of pride.