IPA: /ˈæd.mæn/
KK: /ˈædˌmæn/
A person, usually a man, who creates, writes, or sells advertisements to promote products or services.
The adman came up with a brilliant campaign that increased sales.
Adman is formed from "ad" (from Latin "ad", meaning to or towards) and "man" (from Old English "mann", meaning person). The term refers to a person who works in advertising, indicating someone who is directed towards the field of advertising.
Think of someone who is directed towards advertising ('ad') — that's why an 'adman' is a person in the advertising industry.