morning glory

or morn·ing-glo·ry

noun
  1. any of various plants, especially of the genera Ipomoea and Convolvulus, as I. purpurea, a twining plant having cordate leaves and funnel-shaped flowers of various colors, often opening only in the morning.
  2. a racehorse that runs faster in morning workouts than in afternoon races.

Origin of morning glory

An Americanism dating back to 1805–15
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018