Meaning of four-o'clock family

four'-o'clock fam"ily

Pronunciation: [key]
  1. the plant family Nyctaginaceae, characterized by chiefly tropical herbaceous plants and shrubs having colored, petallike bracts beneath petalless flowers and winged or grooved dry fruit, and including the bougainvillea and four-o'clock.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.