The Collaborative International Dictionary of English v.0.48:
Inflexibleness \In*flex"i*ble*ness\, n. The quality or state of being inflexible; inflexibility; rigidity; firmness. [1913 Webster]WordNet (r) 3.0 (2006):
inflexibleness n 1: a lack of physical flexibility [syn: inflexibility, inflexibleness] [ant: flexibility, flexibleness]