A backer is someone who supports a person, project, or idea, usually by providing money, resources, or public endorsement. When an inventor needs funds to build a prototype, she looks for backers who believe in her vision enough to invest. When a political candidate runs for office, his backers contribute money and time to help him win.

The word suggests more than casual support. A backer puts something valuable on the line: money, reputation, or effort. If you want to start a lemonade stand but need money for supplies, and your neighbor gives you twenty dollars to get started, that neighbor becomes your backer. She's taking a risk that you'll succeed.

In business, backers are investors who fund new companies or products. In the arts, backers support musicians, filmmakers, or theater productions. Successful people often remember their early backers with gratitude, because backing someone means believing in them before others do.

The related word backing refers to the support itself: “With his teacher's backing, the student entered the science competition.” To back someone means to become their backer. When you back a friend's idea in a group discussion, you're lending your voice and credibility to help that idea succeed.