1) a male whose commitment to nudity stops above the waist. 2) a common phenomenon among cartoon characters wherein the character is deprived of pants; see Donald Duck, Ziggy, Winnie the Pooh, etc.
I got invited to go toBurning Man this year, but was scared off by the sheer number of shirtcockers in attendance.
(verb) To walk around wearing a shirt but no pants or undergarments. Synonym of Donald Duck. Technically applies to men only, but plumbing issues aside, easily applies to women, too. Sometimes a mild pejorative, implying imcompleteness or an unwillingness to commit.
A committed nudie who hangs out at hotsprings, burning man, nude beaches, clothing optional clubs etc. who sometimes wears just a t-shirt while his junk is flopping around for all the world to appreciate.
After getting a sunburn on my back, I just went as a shirtcocker the rest of the day.