déclore

An archaic, mostly legal verb meaning to open something that had been sealed or closed off — typically a will ('déclore un testament', the formal act of unsealing it before heirs) or, in older literary French, a garden or enclosure. It's a defective verb like clore: modern usage is almost entirely confined to the infinitive and past participle.

• Le notaire doit déclore le testament devant les héritiers réunis. — The notary must unseal the will in front of the assembled heirs.
• Ce terme juridique, déclore, ne s'emploie presque plus que dans les actes notariés. — This legal term, déclore, is almost only used in notarial documents nowadays.
• Le vieux jardin, longtemps clos, fut enfin déclos au printemps. — The old garden, closed off for a long time, was finally opened up in the spring.

So rare outside legal documents that most native speakers have never used it themselves — a learner is far better off learning ouvrir or lever le scellé for everyday and even most formal contexts.