What is "to pipe in an ivy leaf"

Ivy \I"vy\, n.; pl. Ivies. [AS. [=i]fig; akin to OHG. ebawi, ebah, G. epheu.] (Bot.) A plant of the genus Hedera ( Hedera helix), common in Europe. Its leaves are evergreen, dark, smooth, shining, and mostly five-pointed; the flowers yellowish and small; the berries black or yellow. The stem clings to walls and trees by rootlike fibers.

Direct The clasping ivy where to climb.
--Milton.

Ye myrtles brown, with ivy never sere.
--Milton.

American ivy. (Bot.) See Virginia creeper.

English ivy (Bot.), a popular name in America for the ivy proper ( Hedera helix).

German ivy (Bot.), a creeping plant, with smooth, succulent stems, and fleshy, light-green leaves; a species of Senecio ( Senecio scandens).

Ground ivy. (Bot.) Gill ( Nepeta Glechoma).

Ivy bush. (Bot.) See Mountain laurel, under Mountain.

Ivy owl (Zo["o]l.), the barn owl.

Ivy tod (Bot.), the ivy plant.
--Tennyson.

Japanese ivy (Bot.), a climbing plant ( Ampelopsis tricuspidata), closely related to the Virginia creeper.

Poison ivy (Bot.), an American woody creeper ( Rhus Toxicodendron), with trifoliate leaves, and greenish-white berries. It is exceedingly poisonous to the touch for most persons.

To pipe in an ivy leaf, to console one's self as best one can. [Obs.]
--Chaucer.

West Indian ivy, a climbing plant of the genus Marcgravia.