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3.
A woman and/or man who is typically seen at nocturnal events due to physical and/or mental retardation. Commonly used to recover from past relationship and/or rebounds but are never seen during the day with there partner due to the fact respectable people of there community will see them together and discredit the non-nightbitch.
Ted: How come I only see Lisa at your parties?
Bill: Because shes Tommy's nightbitch.
by ScubaSnow June 06, 2011
 
1.
A dumb inconsderate whore who is with a different guy every day and doesnt care for anyones feelings but themselves.

Sarah Barteck is a fucking NIGHT BITCH
by Uwillneverknomynameiknoutho October 15, 2008
 
2.
A rude person who obsesses over bands such as Nightwish, who write overly-poetic and overly-dramatic lyrics that depressed kids confuse with being beautiful and deep. They more often than not have some kind of deluded crush (or borderline obsession) on keyboardist/lyricist Tuomas Holopainen and suffer from Münchausen by Internet.

Or anyone you dislike who likes Nightwish
You should have known Melissa's a Nightbitch.
by i'm sick of a fat nightbitch June 27, 2010