Tressaillir belong to the 3rd group. Tressaillir is a common french verb.
Tressaillir is conjugated the same way that verbs that end in : -aillir
Tressaillir is conjugated with auxiliary avoir.
Tressaillir verb is
Tressaillir is a french third group verb. So, this verb is irregular and do not follow a regular conjugation pattern like first or second group verbs. Follow this link to see all the endings of the conjugation of most of the third group verbs : conjugation rules and endings for the second group verbs.