Paula Broadwell was (apparently) David Petraeus’ mistress.
What, then, was David Petraeus?
Colloquial English language has no word for that — no label we use to describe the man with whom a married woman cheats. Gigolo doesn’t really cover it. Lover, perhaps, but no newspaper account would use it in a situation like this because their goal is to talk about sex without directly mentioning it. Paramour? That just sounds ridiculous.
Mister-ess? Maybe that will catch on.
The thesis here is that mistress, by virtue of its gender-specificity and possessive nature, paints every extramarital affair the same way, i.e., a sexualized woman seducing a married man. This is a problem, sure, but it’s not one that can be solved by finding a male word for mistress, or even a gender neutral one.
For what it’s worth, we have an agreed-upon narrative for a male seducing a married woman — we usually say “he stole that guy’s wife.” I’m not interested in trying to find a one-word variation on “wife thief,” though. What’s the point? Not only does it still contain the idea of woman-as-property, it would only give us the tools to oversimplify a relationship that was, for better or for worse, extremely complicated.
My primary advice would be to go for the long-form description whenever possible: “Gen Petraeus was having sex with Paula Broadwell even though they were both married.” It’s a mouthful, but at least there’s no room for confusion, no misplacement of blame, no ownership. It’s essentially the least violent way we have to talk about the situation.
If you want the one-word solution, use “affair.” Affair is the king of all euphemisms. It comes from the French “to do,” the most general of all verbs, and can be used in place of most nouns in most sentences. If we’re talking about a relationship that we know almost nothing about, we need a word that says almost nothing. Affair is a word that has almost no meaning — it’s perfect. Plus, our average construction (“they had an affair”) acknowledges a conscious decision by both parties, which puts it squarely ahead of mistress and the like.
Leaving aside whether an affair made public is even worth talking about, we can at least use language that isn’t charged. The rule of thumb is say what you know, no more and no less. And if you don’t know anything, um, what exactly are you saying?