What does the word Gwen mean?

Depends on the context.
According to urban dictionary:
Gwen: adj. describing an attractive female; named after Gwen Stefani
Man, that girl at the club was so Gwen!
Gwen: Verb - To repeatedly fall out of a chair or off of a table
Wow, you just pulled a Gwen.
Gwen:slang for a cigarette progression from cigarette to Cig, cigweno, cigwens, to gweno, to Gwen
"hey bro u got an extra Gwen on u"
Gwen: A slang word used to describe a woman of Asian decent without making racial slurs.
'Gwen gook'
Can be used with the male slang 'Gary'
"Hey that ping pong show was awesome"
"Yeah Gwen was very talented."
or
"There is Gwen, Gary and their son luke gook."