Who's more into sex, men or women? If you were forced to answer, you'd probably have to say men. Not so in the eighteenth century, or for centuries before that. In fact, men were cautioned against having too much sex because it was said to sap precious bodily fluids. Women, on the other hand, were rumored to want it all the time. The worst offenders?
Widows have already had a taste of sex, so they know they like it. Mrs. Wadman is certainly hot to trot. The reason she hesitates to marry Toby is that she's not sure he can function properly in bed, and so her entire life begins to revolve around figuring out the extent of his injury.
As far as we know, Tristram never actually interacts with Mrs. Wadman. We first hear about her in Book 1 when Toby refers to the "shock I received the year after the demolition of Dunkirk, in my affair with the widow Wadman" (1.33.3). But it's not until Book 8 that we finally meet her and get the lowdown on her looks: "never did thy eyes behold, or thy concupiscence covet anything in this world, more concupiscible than widow Wadman" (6.37.5). In other words? She's sexy.
Widow Wadman's pursuit of Toby is supposed to be funny, but it's also another example of one of Tristram's main points: true communication is all but impossible. It would be hard to imagine any two people as different as Toby and the Widow Wadman. Toby is so modest that he never understands the dirty joke, whereas Widow Wadman thinks about nothing but sex. When they try to talk, they can't understand each other because they're each obsessed with something different: Toby with military tactics, and the Widow Wadman with (what else?) penises. Like Susannah, Mrs. Wadman doesn't get the full character treatment that Toby, Mr. Shandy, and even Trim gets. But she's crucial to the story Tristram's telling, because she, like everyone else, is fighting a battle to be understood and to understand. She's a good-looking dame with a heart of gold.