n. One who binds himself to answer for another, and is responsible for his default; a surety.n. One who at the baptism of an infant professes the Christian faith in its name, and guarantees its religious education; a godfather or godmother.n. A person who vouches for another as fit for some post or task.n. A person or group that assumes financial responsibility for some activity, and may or may not participate in its organization and execution.n. A person or organization, usually a commercial organization, which pays the cost of an activity, such as a radio or television broadcast, and in return is given the right to advertise itself or its products as part of the activity.