It is an acronym meaning Wind-Up Merchant.

It refers to someone who posts on message boards and newsgroups with the intention to cause as much disruption as possible by goading others.

Another pronunciation of worm.

Deragatory name for a woman.

= hot
= sexy
= attractive
very duplicitous in its definition

The verb form of WUM (Wind-Up Merchant), a predominantly online phenomena of espousing contrary viewpoints purely to string people along and get a reaction from others. A mild-mannered form of trolling.

"Wum" is the female discharge or female Cum. Womanly cum thus the everyday word WUM.

basically a fucking pussy