The seed from a poppy plant

Its the seed that comes from the Poppy flower.

the most commonly used seed comes from the opium poppy.
wiki says: opium poppy, Papaver somniferum, is the type of poppy from which opium and all refined opiates such as morphine, thebaine, codeine, papaverine, and noscapine are extracted.

poppy seeds found are found in many food items such as bagels, muffins and cakes. The seeds can be pressed to form poppyseed oil, which can be used in cooking, or as a carrier for oil-based paints.

Although the amount of opiates in poppy seeds is not enough to produce a narcotic effect in cooking or consumption, the television show MythBusters demonstrated that one could test positive for narcotics after eating 4 poppy seed bagels.

Me.