the GNU version of the Collaborative International Dictionary of English
n. The quality or state of being thorough; completeness.
The Century Dictionary and Cyclopedia
n. The condition or character of being thorough; completeness; perfectness.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. conscientiousness in performing all aspects of a task
Word Usage
"Yet this conception makes thoroughness a purely _quantitative_ matter; it accepts _thoroughness_ as meaning _throughness_ or completeness, signifying the inclusion of everything from "beginning to end," or from "cover to cover.""