This is the 5003rd most frequent Korean word.
기다리던
"기다리던" means "was waiting for" or "that (someone) was waiting for."
Here, '기다리던' describes '날,' signifying a special day that the speaker has been anticipating.
기다리던 날이 와서 너무 설레요.
The day I was waiting for has come, and I'm so excited.
In this case, '기다리던' modifies '영화,' referring to a specific movie the speaker was awaiting.
기다리던 영화가 개봉했어요.
The movie I was waiting for has premiered.
In this sentence, '기다리던' is used as an adjective that modifies '친구,' indicating that the subject has been waiting for this friend.