"Thin turtleneck" refers to a turtleneck garment made of lightweight or thin material, usually worn on the upper body to cover the neck and provide warmth. Full definition
You could add a mustard yellow tissue thin turtleneck underneath when the weather gets chiller or throw on a cardigan & belt it. (stylishadventures-al.com)
I still find it to hard to find, as a plus size, a nice thin turtleneck, grr. (whenthegirlsrule.com)