[Ed. note: I already beat your warning to the punch, I think. I think the "wide" / "circumference" error is much more common than thought, or at least the assumption in reverse is true. For instance, if someone quoted a measurement of 8" x 2.5," the "jerk reaction" would be -- whoa, you're pretty thin.
Think of it this way. Think of some of the most common uses for the following notation: _____ x _____. We usually see or hear this as a measurement of length and width, most frequently seen in giving room dimensions, fabrics, and other flat objects without a discernible volume to them. Dicks, unlike rooms or material, have a dimension of circumference to them. Well, no shit, right? But since length and width are so "standard" in comparison, hey, we accidentally use an ineffective word. It just happens.]