The phrase "good highlighter" refers to a pen or marker that can be used to mark or emphasize important information in a bright and easily noticeable color. Full definition
One of the millenials» favorites and best highlighters ever, Glossier's Haloscope is a 2 - in - 1 product, perfect both for skincare and makeup. (layow.com)
It also appears to be a bit shinier, which could make it an even better highlighter pen. (theblondeshell.com)