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 09, 2008
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