the GNU version of the Collaborative International Dictionary of English
n. The state of being curvilinear or of being bounded by curved lines.
The Century Dictionary and Cyclopedia
n. The state of being curvilinear, or of consisting in curved lines.
Word Usage
"We suspected that most people would not spontaneously think in terms of this curvilinearity and would, in fact, think that fuel consumption decreases as a linear function of MPG."