What does the term "Domainer" actually mean?

Domainer is commonly used to describe someone that deals in the domain name industry.

As of December 2006 there are an estimated 8,000 to 10,000 individuals globally who make buying and selling domain names a part of their business. USA today reported that many Domainers prefer to remain anonymous due to the highly competitive nature of their business.

A report in USA Today states that known-sales of 5,851 domain names generated $29 million in 2005, compared with known-sales of 3,813 names for $15 million in 2004. Like the tip of an iceberg, the number of reported sales is estimated to be 5-10% of the broader secondary domain resale market.

Domainers can be met at one of the many domain name forums: DNforum.com, Chowcow.com, Namepros.com, etc.

Source: Wikipedia.org