old man's beard

Short definition from Wiktionary

Noun

1. 1
   Chionanthus virginicus, a tree.
2. 2
   Clematis aristata, an Australian climbing plant.
3. 3
   Clematis vitalba, a climbing plant.
4. 4
   Tillandsia usneoides, a bromeliad; Spanish moss.
5. 5
   Usnea, a type of lichen.
6. 6
   Used other than figuratively or idiomatically: see old, man, -'s, beard.