This is the 5683rd most frequent French word.
cassan
The word "cassan" does not have a recognized definition in French. It may be a proper noun, misspelling, or a regional term.
Here, 'cassé' is the past tense of the verb 'casser', meaning 'to break', used to describe the act of breaking something physically.
Il a cassé la branche fragile.
He broke the fragile branch.
In this instance, 'cassé' is used in a reflexive context, 's'est cassé', to indicate that the vase broke as a result of an action.
Le sommet du vase s'est cassé lors de la chute.
The top of the vase broke during the fall.
Here, 'se casse' is the subjunctive form suggesting the possibility of the glass breaking under certain conditions.