a mistake
Having sex with a big woman. Or anything sexual with her. Unless you're the same size. Then it's just fun.
You: "She's huge." Your friend: "You're huge too." You: "We're both huge."
You: "She's like a mountain." Your friend: "You're like a hill." You: "We're both like a mountain."
You: "She's a giant." Your friend: "You're a giant too." You: "We're both giants."