1 at fault | Definition of at fault

fault

noun
\ ˈfȯlt How to pronounce fault (audio) , in poetry also ˈfȯt\

Definition of fault

 (Entry 1 of 2)

1 obsolete : lack
2a : weakness, failing especially : a moral weakness less serious than a vice He loves her despite her many faults.
b : a physical or intellectual imperfection or impairment : defect a theory with some serious faults
c : an error especially in service in a net or racket game She committed too many faults to win the match.
3a : misdemeanor a small boy's faults
b : mistake The misplacement of "only" is one of the most common writing faults.
4 : responsibility for wrongdoing or failure the accident was the driver's fault
5 : a fracture in the crust of a planet (such as the earth) or moon accompanied by a displacement of one side of the fracture with respect to the other usually in a direction parallel to the fracture Frequent earthquakes have occurred along the San Andreas Fault.
at fault
1 : unable to find the scent and continue chase
2 : open to blame : responsible you were really at fault
to a fault
: to an excessive degree precise to a fault