Many words have both legal and non-legal meanings. Genealogists who are not aware of these differences run the risk of misinterpreting a document or a phrase contained in a document. The words in this blog post title are a perfect example.
In the legal sense an infant is someone who is under the age of majority--that age generally where they can perform a variety of acts with no restrictions. Someone who has reached the age of majority is usually able to marry, execute legal documents, etc. State statute determines at what age certain acts can be performed.
In layman's terms "majority" and "infant" mean something else. Make certain you are not confusing them.