I have come across this word through pure coincidence. 3asfour (literal translation of bird) used to have a double meaning in the pre-1950's in Lebanon - it used to mean homosexual. Obviously, the usage of the word for its subliminal meaning has become obsolete (e.g. "Chou 3asfour heyda" meaning how gay is he). 

The funny part about the story is that I have encountered this word with the second/third generation Lebanese whose parents have emigrated in the 20's and 30's to the Americas (in my case to Cuba) and for whom the Lebanese language, slang and day-to-day language have stopped in time! Needless to say that talking to my Lebanese-descent friend in Lebanese was hilarious to say the least :-)

"Msayyaf" or "Msayyfeh", literally means he or she is on summer vacation, but is actually used to describe someone who is unaware of a specific or general situation around them.

 Sample conversation:

Person 1: "everybody in the office knows who the new boss is, except for Gaby"

Person 2: "correct! Gaby Msayyaf!"

"Mesh Ghalat" literally means "it is not wrong", but is used metaphorically to express agreement to an idea. 

 Sample conversation:

Person 1: "What do you say we go to the beach today?"

Person 2: "Mesh ghalat, let us do that!"