Learner's definition of ATTRITION
1 chiefly US : a reduction in the number of employees or participants that occurs when people leave because they resign, retire, etc., and are not replaced
The staff has been thinned through attrition. [=the staff has become smaller because people have left]
Attrition is high among social workers because of the difficult work and poor pay.
a growing attrition rate = a growing rate of attrition
— called also "British"natural wastage
2 : the act or process of weakening and gradually defeating an enemy through constant attacks and continued pressure over a long period of time — used especially in the phrase war of attrition