とば口くち

noun

entrance; threshold

Literally the entrance or doorway of a building; can also refer to the threshold itself. Often used in literary or slightly formal contexts.

• 彼かれはとば口くちに立たって、中なかをのぞき込こんだ。

  He stood at the entrance and peered inside.

noun

beginning; first step; start

Figurative use: the very beginning or outset of something, like standing at the threshold of a new endeavor.

• これはまだ成せい功こうのとば口くちに過すぎない。

  This is still only the first step toward success.