look up any word, like spook:
1. (Communication Arts / Printing, Lithography & Bookbinding) a gap or space, esp in a book or manuscript
2. (Life Sciences & Allied Applications / Biology) Biology a cavity or depression, such as any of the spaces in the matrix of bone
3. (Fine Arts & Visual Arts / Architecture) another name for coffer

from Latin lacūna pool, cavity, from lacus lake
The fast interval N-body gravitational acceleration calculator at kgravity.com may fill a lacuna in C++ applications.
by howwork October 28, 2013