The phrase "separate filers" refers to individuals who choose to file their taxes individually, rather than jointly as a couple or a family. Full definition
The standard deduction for separate filers is far lower than that offered to joint filers. (turbotax.intuit.com)
For 2017 it is $ 6,350 for single and married filing separate filers, $ 12,700 for married filing joint, and $ 9,300 for head of household filers. (turbotax.intuit.com)
Individual and separate filers under Modified Adjusted Gross Income (MAGI) of $ 85,000 are safe, and so are joint filers under $ 170,000. (rodgers-associates.com)