Definition of "sundress"

I'm in his favorite sundress, watching me get undressed

2011, Lana Del Rey, Justin Parker (lyrics and music), “Video Games”

The brand, in its collaboration with Target, provoked ire—proving that, in the right circumstances, even sundresses can be part of the culture wars.

2015 April 22, Megan Garber, “Why Do People Hate Lilly Pulitzer?”, in The Atlantic‎