The phrase "trim line" refers to the outer edge or boundary of something, usually a surface or object. It indicates where the excess or unwanted parts are removed or cut off to achieve a desired shape or appearance. Full definition
The navigation - equipped Fit is also the only trim line with HD Radio and satellite radio even though each has a small chipset cost. (extremetech.com)
Rear parking sensors and rear cross traffic alert supplement the camera on higher trim lines. (extremetech.com)
In contrast, many competitive midsize sedans offer these features only in the top trim line models. (thetorquereport.com)