The adjective used to describe someome who signs in on MSN, realizes that their ex Girlfriend/someone else they don't want to talk to is online. Thinking "Oh, crap!" They appear offline, and talk to people they do want to, without being spotted.
OLLIE: Hey man, what you up to?
SAM: Not much... Hey I thought you were offline?
OLLIE: Nah mate, Lauren is on, I'm just pretending to be offline so she doesn't get up me.
SAM: Oh, I see, going MSN ninja. Good idea.
SAM: Not much... Hey I thought you were offline?
OLLIE: Nah mate, Lauren is on, I'm just pretending to be offline so she doesn't get up me.
SAM: Oh, I see, going MSN ninja. Good idea.
by John Hylius June 15, 2009
One who seldom or never shows him/herself on MSN by appearing offline. MSN Ninja's are very selective of who they choose to be seen by, and just like a ninja, can disappear just as easily as they appear.
by Jerry the Hairy Berry October 9, 2008