Failing has 7 different meanings across 4 categories:
Noun · Adjective · Prep · Proper Noun
weakness; defect
"The old bridge had structural failing that made it unsafe for heavy trucks."
present participle of fail
"The failing engine made it difficult to start the car on a cold morning."
In plain English: To fail means to not succeed at something you were trying to do.
"The plan is failing because we do not have enough money to pay for supplies."
if the preferred or prior option is not possible
"When our primary supplier stopped shipping, we had no choice but to proceed with failing to find an alternative vendor immediately."
A surname.
"The Failing family has lived in that village for three generations."