defining moment
Noun
Meaning
A moment in time that defines something, such as a person's success or failure, achievement or demise, talent, etc.
A point at which the essential nature or character of a person, group, etc., is revealed or identified.
Source: en.wiktionary.orgSynonyms
rubicon
high noon
crunch
climacteric
watershed
crossroads
critical point
point of no return
moment of truth
critical mass
breaking point
match point
road to Damascus