Translation

こっそり動く / 忍び込む / こっそり持ち出す

Meaning

To move somewhere quietly and secretly, often to avoid being seen or heard. It can also mean to bring or take something somewhere without anyone noticing.

Examples

• He tried to sneak out of the house without his parents noticing.
  彼は両親に気づかれないようにこっそり家を抜け出そうとした。
• She managed to sneak a cookie from the jar before dinner.
  彼女は夕食前にこっそり瓶からクッキーを盗み食いした。