tipping point

Short definition from Wiktionary

Noun

1. 1
   The point at which a slow, reversible change becomes irreversible, often with dramatic consequences.
2. 2
   A point in time when a group rapidly and dramatically changes its behavior by widely adopting a previously rare practice.
3. 3
   A point in time when a group rapidly and dramatically changes its behavior by widely adopting a previously rare practice: The point in time at which some new technology becomes mainstream.
4. 4
   An irreversible change in the climate system.