a person or thing that promotes, furthers, or encourages.

a person who initiates or takes part in the organizing of a company, development of a project, etc.

a person who organizes and provides financial backing for a sporting event or entertainment.

Chemistry . any substance that in small amounts is capable of increasing the activity of a catalyst.

Also called collector. Metallurgy . a water-repellent reagent enhancing the ability of certain ores to float so that they can be extracted by the flotation process.

Genetics .

a site on a DNA molecule at which RNA polymerase binds and initiates transcription.

a gene sequence that activates transcription.

Obsolete . an informer.

noun

advertiser , advocate , ally , backer , booster , endorser , follower , organizer , publicist , sponsor , agent , lobbyist , proponent , supporter