point of no return

plural points of no return

1. aeronauticsThe point in an aircraft's flight when there is insufficient fuel to reverse direction and return to the place of origin.

   Synonyms: event horizon, PNR, PONR, rubicon, threshold

2. figurativelyThe point in any process or sequence of events where some development becomes inevitable.

   After Munich it became daily more evident that Hitler had passed the point of no return. With every burst of news from Europe the inevitability of war became more certain.

   1959, Roger Burlingame, I Have Known Many Worlds, page 216

   3 more examples

   [...] this trickle of loss going on relentlessly week by week will gradually reduce miscellaneous merchandise loadings on the railways to a point of no return, where the entire business must be abandoned to cut steeply mounting losses.

   1964 May, “News and Comment: Liner trains and the NUR”, in Modern Railways, page 290

   However, for slightly larger stars, no such final equilibrium state is possible, and in such a case the star will contract beyond a certain critical point — the point of no return — where complete gravitational collapse leading to a spacetime singularity is inevitable.

   1999, Malcolm Ludvigsen, General Relativity: A Geometric Approach, page 152

   A record loss of sea ice in the Arctic this summer has convinced scientists that the northern hemisphere may have crossed a critical threshold beyond which the climate may never recover.

   2005 September 16, Steve Connor, “Global warming 'past the point of no return”, in The Independent, archived from the original on 15 Jan 2007