Pronunciation: (u-nas"tu-mō'sis), [key]
—pl. -sesPronunciation: (-sēz). [key]
1. Anat.communication between blood vessels by means of collateral channels, esp. when usual routes are obstructed.
2. Biol., Geol.connection between parts of any branching system, as veinlets in a leaf or branches of a stream.
3. Surg., Pathol.a joining of or opening between two organs or spaces that normally are not connected.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.