"Weed killer" refers to a substance that is used to get rid of unwanted plants or weeds in gardens or lawns. It helps in eliminating or preventing the growth of these plants, keeping the area clean and free from unwanted vegetation. Full definition
Short answer: Yes, there are traces of weed killer in many types of oatmeal. (health.com)
I didn't know it at the time but she had eaten some grass that had just been sprayed with weed killer in my next door neighbors yard. (whole-dog-journal.com)