A more thorough explanation:

Definition: To enter into a marriage, contract, or other formal agreement by performing a ceremony, usually in front of witnesses.

Example 1: The couple decided to solemnize their marriage in a church with all their family and friends present.

Example 2: The company will solemnize the signing of the contract with a formal ceremony attended by all parties involved.

Example 3: The judge solemnized the adoption of the child by signing the necessary legal documents.

These examples illustrate how solemnize is used to describe the act of making a formal agreement official through a ceremony or legal process. In each example, there is a formal act that is being performed in front of witnesses to make the agreement official.