Waistline/ˈweɪstlaɪn/ Definition 1 of 3Pro Tip 1/3Body Positivity Discussing someone's waistline can be sensitive; use the term respectfully due to body image issues. She's proud of her waistline after working out. Pro Tip 2/3Healthy Lifestyle The term often relates to fitness and health, addressing changes due to diet or exercise. His waistline shrank after he started cycling. Pro Tip 3/3Fashion Fitting In fashion, waistline can imply a preferred size or the need for tailoring clothes. I need to adjust my pants' waistline for a better fit.