Grossir belong to the 2
nd group. Grossir is a common french verb.
Grossir is conjugated the same way that verbs that end in :
-ir
Grossir is conjugated with the two auxiliaries
être and
avoir.
Grossir verb is
direct transitive, intransitive.
Grossir verb is a direct transitive verb, so passive voice can be used.
Attention: passive voice can only be used when grossir verb is conjugated with auxiliary avoir.