Definition
to accompany a person or group to a place, typically without being invited
跟屁股（未经邀请）
She wasn't invited, but she decided to tag along with her friends to the party.
她没有被邀请，但她决定跟朋友一起去派对。
The little brother wanted to tag along with his sister, but she just wanted to be alone with her friends.
弟弟想跟着姐姐一起去，但她只想和朋友单独相处。
Even though I hadn't planned to go out, my curiosity led me to tag along when my colleagues went to lunch.
虽然我原本没打算出去，但好奇心驱使我跟同事们一起去吃午餐。