Denshi Jisho — Online Japanese dictionary

内緒 ないしょ 1: secrecy; confidentiality; privacy; secret;
2: one's circumstances (esp. fiscal)
Common word, Noun, No-adjective 
内緒 ないしょごと secret; private or confidential matter
Noun 
内緒 ないしょばなし secret talk
Noun 

You can also

Look up kanji details for 内緒.

Try a Yahoo Jisho search for 内緒 .
Try a Goo Jisho search for 内緒 .
Try a Google search for 内緒 .