lacuna \luh-KYOO-nuh\, noun;
plural lacunae \luh-KYOO-nee\ or lacunas::
1. A blank space; a missing part; a gap.
2. (Biology) A small opening, depression, or cavity in an anatomical structure.
Like most other writers of his generation, he was a profoundly apolitical being, not from any lacuna in his education but as a matter of principle.
-- Walter Laqueur, "The Artist in Politics", New York Times, May 15, 1983