crématiser

Crématiser is an extremely rare, technical verb occasionally used in specialized writing about cremation processes — in ordinary French, incinérer or the noun phrase crémation (with a form of faire) is what's actually used, both in speech and in most formal writing.

• Le corps a été crématisé selon ses dernières volontés. — The body was cremated in accordance with his final wishes.
• Ce four est conçu pour crématiser plus rapidement. — This furnace is designed to cremate more quickly.
• La loi encadre strictement la façon de crématiser un défunt. — The law strictly regulates how a deceased person may be cremated.

This word is so rare that most native speakers would default to incinérer or faire crématiser instead — a learner is far more likely to need those than crématiser itself.