(noun)
a cosmetic make-up product that is applied to the lips to make them appear shiny, and which may or may not have a color/tint;
e.g. She applied a pink gloss to her lips.
(noun)
an appearance or impression of brightness or attractiveness, especially one that is deceptive and/or only superficial;
e.g. Beneath the gloss of being a celebrity, many actors struggle with feelings of anxiety or insecurity.
(verb)
to apply a shiny substance such as paint or polish to a surface in order to make it appear smooth and glazed;
e.g. If you gloss the pottery, it will appear bright and shiny.
(verb)
to be deceptive in dealing with something, such as to mask its true nature/appearance and make it seem attractive or to address an issue too casually or not at all (used as "gloss over" in both cases);
e.g. He tried to gloss over his struggles because he did not want to worry them.