PMI has defines the project as single effort undertaken in order to create unique project or service. To what extent do you agree with this ?

The definition given by PMI is correct.

Dear Asim,

Yes i agree to PMI project defination because resources are utilized once to produce/create initially for business solution or need. After delivery of project/service it becomes operational.

Resources are engaged to work/use it on repeated manner. Simply we can say single activity by resources is needed to create Project/Service.