Standby
On Call
noun, verbal noun, の adjective
A waiting machine is a machine on standby. This word doesn’t always apply to machines though. It could be a person who’s on standby, in which case you might also say they’re on call.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
家で待機するように言われてたんだけど、こっそり外出してマクドナルドでハンバーガーを買ってきちゃった。
I was told to stand by at home, but I snuck out and got a hamburger at McDonald's.
トーフグのエンジニアは、いつでもワニカニのバグに対応できるよう、常に待機している。
Tofugu engineers are always on call to respond to any WaniKani bugs.
少子化なのにどうして待機児童が増えるんですか？
If birth rates are declining, why are waitlists for schools increasing?