It looks like a very young Canada thistle plant to me..and the only
thing that I have found to kill it is fresh roundup. ISTM that when
Roundup gets older it loses it's punch.

You can also get rid of it by digging it up. In my soil I cannot pull it
up..it just breaks off.

EJ in NJ

wrote:
This weed, which we call "The Tumor" (in your best Arnold
Schwartzenager voice) is drivng us nuts. It comes on super fast,
grows super fast and returns after we pull it out. Its got prickly
edges. See phot link below.

Is there a chemical based weed killer that can take this out? Preen
did nothing to it. This weed just laughed at Preen.

http://ucemergencymedicineorg.siteprotect.net/weed.jpg