It's a weed grass. Hard to say which species exactly but likely Yorkshire fog or a Timothy variant. They can be carefully pulled or grubbed out with a dandelion grubber. Failing that, a weak glyphosate solution applied to the leaves will kill it off but a bit of ground prep and reseeding will be required.
They stand out more at this time of year because they are desperately trying to seed, so grow a lot faster.