parallel vertical lines with dark shading over the head or under the eye may represent mortification, fatigue, or horror. if the lines are wavy, they may represent disgust. a far cuter way to represent frustration/mortification is (mainly for female/young female characters) that they tend to puff out their cheeks while their line is delivered in a gruff voice, an elongated "3" showing puffed lips, to emphasize that puffed look.