Loco \Lo"co\, n. [Sp. loco insane.]
1. (Bot.) A plant ({Astragalus Hornii}) growing in the
Southwestern United States, which is said to poison horses
and cattle, first making them insane. The name is also
given vaguely to several other species of the same genus.
Called also {loco weed}.
[1913 Webster]
2. (Bot.) Any one of various leguminous plants or weeds
besides {Astragalus}, whose herbage is poisonous to
cattle, as {Spiesia Lambertii}, syn. {Oxytropis
Lambertii}.
[Webster 1913 Suppl.]