One who assumes responsibility for another person or a group during a period of instruction, apprenticeship, or probation, A legislator who proposes and urges adoption of a bill, One that finances a project, event, or organization directed by another person or group, such as a business enterprise that pays for radio or television programming in return for advertising time, verb_ assume responsibility for or leadership of, do one's shopping at; do business with; be a customer or client of, transitive To be a sponsor for