a person or organization that pays for a project or activity, e.g.:
somebody who pays towards the cost, or part of the cost, of a cultural or sporting event
somebody who contributes towards a charity by giving money for a participant's efforts in an organized fund-raising event, e.g. a sponsored walk
chiefly NAmer somebody who pays the cost of a radio or television programme, usu in return for limited advertising time during its course
a person who presents a candidate for baptism or confirmation and undertakes responsibility for his or her religious education or spiritual welfare; a godparent
somebody who introduces and supports a bill, motion, etc in parliament
somebody who assumes responsibility for some other person or thing
sponsorial /sponʹsawri·əl/ adj
sponsorship noun
[Latin sponsor guarantor, surety, from spondēre to promise]