That appears to be another species of grass.
Dig out the clumps with a shovel, top dress with good soil and overseed using a quality grade one grass mix suitable for your region.
When some-one here tells you to use round-up, consider that the chemical will kill any-thing growing and you have to wait for the clump to die down. That could take a few days,and it has to be 70 ferenheit for a few days to make it work properly. Then you have to dig out the dead clump any how.
Save your money and just dig it as I have suggested. Then it's done.