noun

1. a person or agency that undertakes certain responsibilities in connection with some other person or some group or activity, as in being a proponent, endorser, advisor, underwriter, surety, etc.
2. 1. a godfather or godmother; person who answers for a child, as at baptism, making the profession of faith and the promises prescribed
   2. in some Christian denominations, a person who acts as patron for someone being confirmed
3. ☆ a business firm or other agency that alone or with others pays the costs of a radio or television program on which it advertises or promotes something

Etymology: L, surety < spondere, to promise solemnly < IE base *spend-, to bring a libation, vow > Gr spendein, to promise, spondē, libation

transitive verb