| Noun | 1. | ram's horn - annual of southern United States to Mexico having large whitish or yellowish flowers mottled with purple and a long curving beakherb, herbaceous plant - a plant lacking a permanent woody stem; many are flowering garden plants or potherbs; some having medicinal properties; some are pests genus Proboscidea, Proboscidea - in some classifications included in the genus Martynia and hence the two taxonomic names for some of the unicorn plants | |