Rassir is a defective verb.
This verb only exists in infinitive, in past participle and past gerondive.
Here are several examples of defectives verbs:
bruire,
distraire,
traire,
extraire,
soustraire,
paître.
Rassir verb is conjugated in female form and in reflexive form. Be careful, the past participle of compound tenses must agree with the subject.
Finally, the interrogative form does not exist in subjunctive and imperative.