What is meant by outliers in text data set. How to detect them?
I define an outlier in the following ways.


It can be a wrong data entry (Eg. human typing error)
It can be a data that has values that are not relevant (Eg. an entry of total which is calculated as the sum of the above columns. This data can be misleading at times so it should be removed)
It can be a data entry that is all or most fields blank (Eg. a row in the data where all fields are blank. This row maybe not contributing anything to the analysis)
It may be extreme values which fall way out of the range of the other data (Eg. when we are calculating the age of Humans, anyone with age (say) above 120 years is an extreme case and that can be ignored depending upon our analysis goal)