You need to post your request on; Name this Plant.

Yes, the 'Name this Plant' forum is very good about naming plants.

However, I guess what you really need to know is how to eliminate it from your lawn. It looks like a broad leaf weed as opposed to a grass weed. You can spray the lawn with a broad leaf weed killer which is available at garden centers and big box stores. Read the directions carefully and spray on a non windy day so it won't drift onto desirable broad leaf plants you may have growing in your yard. Good luck!