lo·co·weed / ˈlōkōˌwēd/ • n. 1. a widely distributed plant (genera Astragalus and Oxytropis) of the pea family that, if eaten by livestock, can cause a brain disorder, the symptoms of which include unpredictable behavior and loss of coordination. 2. inf. cannabis.

locoweed Astralagus and Oxytropus spp., common in arid areas of the western USA. Toxic to cattle, causing locoism: neurological damage, abortion, and birth defects. Apparently caused by an alkaloid, swainsonine, which is also found in mouldy hay.