This is the 10078th most frequent French word.
grossier
Rude, coarse, or uncivil.
In this sentence, 'grossier' describes a behavior that lacks refinement or manners, specifically talking with a full mouth.
Il est grossier de parler la bouche pleine.
It is rude to talk with your mouth full.
Here, 'grossier' is used to indicate something that is not finely done or polished, referring to the quality of the work.
Son travail est encore un peu grossier, mais prometteur.
His work is still a bit rough, but promising.
In this case, 'grossier' is characterizing an impolite or offensive action, specifically the nature of the response given.