on sight

1. idiomaticImmediately when sighted.

   I recognized him on sight.

   3 more examples

   "Permissive" working allows more than one train to be in a block section at one time but trains must be run at low speed in order to stop on sight behind the train in front. Such working is often authorised to allow freight trains to "bunch" together to await a path through a bottleneck instead of being strung out over several block sections, as would be necessary if absolute working were in force.

   1962 October, “Talking of Trains: The collisions at Connington”, in Modern Railways, page 232

   If you were to examine a standard nipple clamp, you would find it resembles a pair of tiny alligator jaws and with good reason – Earl’s first nipple clamps were a pair of live baby alligators trained to bite nipples on sight.

   2005, Annabelle du Fouet, “Toys for kinky girls and boys—It’s not just whips and chains anymore.” (chapter 3), in Weather Balloons Make Rotten Sex Toys, Ellora's Cave, →ISBN, page 54

   Somewhat unsurprisingly, unleashing the most powerful navy on the planet with carte blanche to exterminate slavers on sight saw a dramatic and sudden collapse in slaver numbers in the late 1840s and early 1850s.

   2018 December 1, Drachinifel, 10:12 from the start, in Anti-Slavery Patrols - The West Africa Squadron, archived from the original on 29 Nov 2024

2. broadlyImmediately upon coming to one's attention.

   He dismissed the idea on sight.

3. broadlyslangcause for a fight, immediately upon encounter without deliberation.

   If he keeps talking crap about me, its on sight.

plural on sights

1. climbingAn ascent of a route without falling, on the first attempt, without having been advised on it or having seen it prior.