Synonyms for Spanish Dagger (same or very similar meaning)
WordNet sense 1 (yucca of southeastern United States similar to the Spanish bayonets but with shorter trunk and smoother leaves):
Yucca gloriosaWordNet sense 2 (arborescent yucca of southwestern United States and northern Mexico with sword-shaped leaves and white flowers):
Yucca carnerosanaFrom the ODE community, based on WordNetadd/edit