This is the 9961st most frequent Japanese word.
走り出し
The Japanese word "走り出し" means "the act of starting to run."
Here, "走り出す" pertains to the act of initiating running, focusing on the speed at which this action begins.
彼の走り出すスピードは驚くべきものだった。
His starting speed when running was astonishing.
The word "走り出し" is used as "走り出した" here, indicating the action of starting to run or move forward.
列車が走り出した。
The train started running.
In this sentence, "走り出し" conveys the beginning of the activity of running, in this case toward the park.