look up any word, like half chub:
 
1.
A totally badass girl. Always there for her friends and always giving great advice. An Onnie is very very cute, with a little ski-sloped nose and blonde hair. Boys always fall in love with her. They generally have an awesome best friend named Lisa and a really cute boyfriend named David. Onnies are always up for an adventure; whether its streaking, raving, or committing grand theft auto, shes always there with a pair of stunnah shades and a positive attitude.
Josep- "Dude I totally wanted a one night stand with this girl I met at the party last night...."

Sam- "Well, what happened man?"

Josep- "I fucked her, but then I accidentally fell in love with her... so I called her back."

Sam- "Ahh... yeah, she's an Onnie huh?"
by VanillaTwilight March 01, 2010