say it: STIF-nuhs
stiffness is a noun meaning "the physical property of being inflexible and hard to bend". It carries 5 recorded senses.
the physical property of being inflexible and hard to bend
the property of moving with pain or difficulty
“he awoke with a painful stiffness in his neck”
firm resoluteness in purpose or opinion or action
“a charming host without any touch of stiffness or pomposity”
the inelegance of someone stiff and unrelaxed (as by embarrassment)
excessive sternness
“severity of character”
“the harshness of his punishment was inhuman”
“the rigors of boot camp”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for stiffness come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.