The canonical definition of "schism" is "the refusal of submission to the Supreme Pontiff or of communion with the members of the Church subject to him."
A priest who fully adheres to all the dogma of the Church, yet fails to submit to the lawful authority of the pope, is in (at a minimum) material schism.
In 2009, Pope Benedict, in his motu proprio Ecclesiae Unitatem, declared: "However, the doctrinal questions obviously remain and until they are clarified the Society has no canonical status in the Church and its ministers cannot legitimately exercise any ministry."
Earlier, the pontifical commission Ecclesia Dei clarified in a letter: "There is no doubt about the validity of the ordination of the priests of the Society of St. Pius X. They are, however, suspended a divinis, that is, prohibited by the Church from exercising their orders because of their illicit ordination."
In spite of the indults granted by Pope Francis (for the benefit of the faithful) allowing SSPX clergy to hear confessions and officiate weddings on certain conditions, the official status of the SSPX has not changed. They have no canonical status in the Church, and they remain suspended a divinis.
In 2013, Cdl. Gerhard Müller, then-prefect of the Congregation for the Doctrine of the Faith, said of the Society of St. Pius X (SSPX),
The canonical excommunication of the bishops for their illegal ordinations was revoked, but a de facto sacramental excommunication remains for their schism; they put themselves out of communion with the Church.
Cardinal Raymond Burke, former prefect of the Apostolic Signatura, the Church's highest court, recently confirmed their status.
[T]he fact of the matter is that the Priestly Society of St. Pius X is in schism since the late Abp. Marcel Lefebvre ordained four bishops without the mandate of the Roman Pontiff. And so it is not legitimate to attend Mass or to receive the sacraments in a church that's under the direction of the Priestly Society of St. Pius X.
Watch the panel respond to objections and clarify issues in The Download—Schism.