on call

Idioms  

1. Available if summoned, as in Medical residents are required to be on call at least three nights a week. This expression originated as at call in the late 1500s. Also see at someone's beck and call.

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Example Sentences

Lawyers say the trade court keeps a judge on call to act quickly when parties come to court seeking an emergency intervention and that was likely how the refund issue ended up in Eaton’s lap.

From The Wall Street Journal • Mar. 14, 2026

While he worked with Rojas, Battle’s complaint alleges, she required him “to be on call 24/7” and do her personal errands.

From Los Angeles Times • Mar. 8, 2026

New rules will mean reservists remain on call for an extra decade, and lower the threshold for them being called into service.

From BBC • Jan. 15, 2026

Just having an adviser on call — even if you’re only paying for their time to deliver occasional services — can be valuable.

From MarketWatch • Oct. 9, 2025

Several months ago the affiliate here in Birmingham asked us to be on call to engage in a nonviolent direct-action program if such were deemed necessary.

From "While the World Watched: A Birmingham Bombing Survivor Comes of Age during the Civil Rights Movement" by Carolyn Maull McKinstry