Cantonese slang, "lun" refers to penis, "yeung" refers to face. thus, "lun" + "yeung" = penis-face

equivalent in measure with the American term of calling someone an "asshole"
Colman: How was your take home physics exam?
Jeff:Dave that "lun yeung" messed up the calculations.
by The Diuler September 18, 2007
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