Doorway
noun
A door's mouth is the doorway!
戸口 is mostly used for doorways that lead outside. It has an old-fashioned feel to it and is becoming less common these days, especially in spoken Japanese.
You might notice that this word resembles 出口 (exit) and 入り口 (entrance). Like in those words, the character 口 just represents an opening here.
The reading for this one is mixed. You get the kun'yomi readings for both kanji, even though it's a combo (jukugo) kanji. Since 戸's only reading is the kun'yomi reading you should know it. Also, you should know the kun'yomi reading for 口 as well from level 1. That means as long as you remember that this is a kun'yomi fest over here, you should be able to read this word. Also watch out for the rendaku (also known as sequential voicing). That just means the く becomes the voiced ぐ.
このアパート、戸口のデザインがかわいいですね。
The design of this apartment's doorway is cute.
この戸口、少し小さいね。
This doorway is a little small.
なんで、ずっと戸口に立ってるの？
Why are you always standing in the doorway?