a parody of the phrase "when in Rome, do as the Romans do", this phrase means ( used in a nice, non-belliugerent way):

"if you want to integrate into, and be a part of, polite society, behave, as a rule of thumb, like most other people of your age, gender and/or social status behave in your society in your zeitgeist"
a boy with almost no friends comes home from high school and starts conmplaining to his father:

boy: dad, why don't i have any friends my age?

father: pragmatically speaking, Brandon, I thing you are not applying correctly my famous cherry-phrase "when in Rome, speak Latin." IMHO it's doesn't take Albert einstein to figure out why you have no friends: you don't do, at least after school, what most other boys your age are doing. All you do after class is watch porn, argue with your mother and sisters as to whether or not to do your chemistry, and help Mr. and Mrs. Philips, our generous elderly neighbors, with their gardening.

boy: But that's what I have always done. Wait so you have contradicted yourself, because humans are creatureses of habit, psychologically and biologically speaking.

father (ignoring Brandon's interruption): However, most boys your age, after class, date their girlfriends, play football and maybe monkey hoops, play the saxophone or another musical instrument a la Lisa Simpson, maybe hang out with their friends and look for trouble a la Bart Simpson and Nelson Muntz, maybe even play marbles. Some young men your age even go to bars/clubs and get a refreshing drink after a hard day's work. Go and do some of the things I've mentioned and you'll make friends tic-tac-toe

boy: (imitating homer simpson): D' Oh. so no wonder then I feel and act like a white crow
by Sexydimma February 23, 2012
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