What does 秘密 (mì mì) mean in English?

Card 659HSK 2010 Level 5659/1311
CARD659
PROGRESS50%
秘密
mì mì
secret; CL:個|个[ge4]
Click to reveal
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Reveal: Click/Space/Enter/↑↓/w/s/j/k•Navigate: ←→/h/l/a/d