"卖萌"，在实际网络中一般可以理解为，装可爱，刻意出现一些可爱的动作、言语等。
http://baike.baidu.com/view/3057625.htm
"卖萌" is to pretend to be cute.
The verb “pretend” has a few synonyms: affect, assume, feign, etc.
To pretend is to create an imaginary characteristic or to play a part: to pretend sorrow.
To affect is to make a consciously artificial show of having qualities that one thinks would look well and impress others: to affect shyness.
To assume is to take on or put on a specific outward appearance, often (but not always) with intent to deceive: to assume an air of indifference.
To feign implies using ingenuity in pretense, and some degree of imitation of appearance or characteristics: to feign surprise.
http://dictionary.com/
