The word "skirt" clearly has two meanings.

One meaning is generic and describes any kind of tubular hanging object, like the skirt of a car, jacket, or other similarly-configured item of clothing. Using that very generic definition a kilt is indeed a skirt.

The other meaning is the description of a specific type of clothing. In that meaning, a "skirt" is a female garment that hangs from the waist.

A kilt is a skirt.

A kilt is not a skirt.

So, when someone on the street says, "Hey, nice skirt." I have to quickly discern whether they mean the generic sense of "skirt" or if they are attempting to imply that I'm wearing women's clothing.

I look for the smart-a** smirk. If I see the smirk, I correct the person by saying, "It's a kilt, but thank you."

Otherwise, I just say, "Thank you," and smile.