alarm bell

plural alarm bells

1. figurativelyplural normallyA sudden awareness of danger.

   I only got a glimpse of him, but alarm bells went off. He wasn't rushing over to give me a pat on the back for stopping to help.

   2010, John M Findley, Just Lucky

   4 more examples

   The specter of women in factories, women in schoolrooms, and women attending — a lot less addressing — public meetings set off alarm bells in the South.

   1998, Michele Gillespie, Catherine Clinton, Taking off the white gloves: Southern women and women historians

   England were shipping penalties at an alarming rate - five in the first 15 minutes alone - and with Wilkinson missing three long-distance pots of his own in the first 20 minutes, the alarm bells began to ring for Martin Johnson's men.

   2011 October 1, Tom Fordyce, “Rugby World Cup 2011: England 16-12 Scotland”, in BBC Sport

   The December 11 Telegraph story, which accused the Treasury of blocking plans for £30 billion worth of electrification across the rail network [...], has rung alarm bells over who is the real source of power concerning rail's development - the Department of Transport or the Treasury?

   2022 January 12, Tom Allett, “MPs concerned at Treasury's influence on rail industry”, in RAIL, number 948, page 13

   That an arch-election denier who has been at the forefront of attempts to overturn Biden’s victory should refuse to state openly whether she will abide by the outcome of her own election has set alarm bells ringing.

   2022 November 2, Ed Pilkington, “‘The Trump playbook’: Republicans hint they will deny election results”, in The Guardian

2. Used other than figuratively or idiomatically: see alarm, bell.

   He put his foot on a concealed button under his desk and rang an alarm bell. He always had two strongarm men lolling around in an office down the passage.

   2000, James Hadley Chase, An Ear to the Ground