the world > plants > part of plant > reproductive part(s) > flower or part containing reproductive organs > inflorescence or collective flower > [adjective] > having only one head (2)
Of flowers: Having only one whorl or set of petals; also, of plants: Bearing such flowers; opposed to double, adj.1 1d.
Botany. Of a stem, stalk, etc.: bearing a single capitulum or umbel. Of a plant: having its flowers in a single capitulum or umbel.