天机不可泄露

1. • lit. mysteries of heaven must not be revealed (idiom) must not be revealed
2. • I am not at liberty to inform you.

Character by character

• 天(tiān)day
• 机(jī)surname Ji
• 不(bù)no
• 可(kě)can
• 泄(xiè)leak out
• 露(lù)surname Lu