A more thorough explanation:

Cy pres is a legal term that means "as near as." It is an equitable doctrine used by courts to reform a written instrument with a gift to charity as closely to the donor's intention as possible, so that the gift does not fail. This is done when the donor's original charitable purpose cannot be fulfilled.

For example, if a donor leaves money to a charity that no longer exists, the court may use cy pres to distribute the money to a similar charity that will advance the interests of the donor. Another example is when unclaimed portions of a class-action judgment or settlement funds are distributed to a charity that will benefit the class.

Cy pres can also refer to a statutory provision that allows a court to reform a will, deed, or other instrument to avoid violating the rule against perpetuities. The rule against perpetuities is a common-law rule that prohibits a grant of an estate unless the interest must vest, if at all, no later than 21 years after the death of some person alive when the interest was created.

For example, if a donor leaves property to their great-great-grandchildren, the court may use cy pres to reform the will so that the property is distributed to the donor's living relatives instead. This is done to avoid violating the rule against perpetuities.