私下

私下	sī xià	in private
私	sī	(bound form) personal; private / (bound form) selfish / (bound form) clandestine / (bound form) illicit / (Internet slang) to send a private message to sb
下	xià	down / downwards / below / lower / later / next (week etc) / second (of two parts) / to decline / to go down / to arrive at (a decision, conclusion etc) / measure word to show the frequency of an action