n. The characteristic of being indispensable; indispensability.
the GNU version of the Collaborative International Dictionary of English
n. The state or quality of being indispensable, or absolutely necessary.
The Century Dictionary and Cyclopedia
n. The state or quality of being indispensable or absolutely necessary.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the quality possessed by something that you cannot possibly do without
Word Usage
"A constitutional conservatism puts liberty first and teaches the indispensableness of moderation in securing, preserving and extending its blessings."