The Oxford Thesaurus An A-Z Dictionary of Synonyms - backern.

1) supporter, advocate, promoter, sponsor, patron: She has always been an enthusiastic backer of adult education. 2) investor, benefactor or benefactress, supporter, underwriter, Colloq angel: The play's backers have made huge profits. 3) bettor, Brit punter: His backers are offering odds of 10 to 1.