Opponents of same-sex marriage have discovered to their chagrin that two major English dictionaries have revised their definitions of marriage to reflect changes in the way that people have been using the word.

Merriam-Webster acknowledged the increased discussion among supporters and opponents of gay and lesbian marriage in recent years by adding this section to its earlier definition of marriage: "(2): the state of being united to a person of the same sex in a relationship like that of a traditional marriage." The dictionary made that change in 2003, one year before Massachusetts became the first state to legalize same-sex marriage.

The Oxford English Dictionary definition of marriage has included same-sex couples since 2000: "The term is now sometimes used with reference to long-term relationships between partners of the same sex." The OED's earliest citation comes from the New York Times in 1975: "The move toward legally-sanctioned marriages between persons of the same sex." 

Above: the entry for marriage from Merriam Webster's online dictionary. Below, excerpt from the OED definition and the earliest citation of the term 

Opponents of same-sex marriage view these new definitions as a part of the concerted left-wing-gay-lesbian-lexicographical plot to undermine family values in America. According to the conservative World Net Daily, "One of the nation's most prominent dictionary companies has resolved the argument over whether the term 'marriage' should apply to same-sex duos or be reserved for the institution that has held families together for millennia: by simply writing a new definition."

But new definitions don't find their way into dictionaries like Merriam-Webster's or the OED to promote a political agenda. Nor do revised definitions change what words like marriage mean. Instead, lexicographers write their definitions to reflect how people actually use the words of English, not how special-interest groups want them used, and lexicographers periodically update these definitions when enough people start using a word or phrase in a new way.

The lexicographer's job is to watch for language change. So far as marriage is concerned, it doesn't matter whether supporters or opponents of same-sex marriage use the term, so long as they both use it to refer to the marriage between two people of the same sex. That means that supporters of California's Prop 8 – the activist opponents of same-sex marriage – have contributed to the new definition they're complaining about by simply repeating the phrase so often themselves.