hardening in WordNet English dictionary

1. the process of becoming hard or solid by cooling or drying or crystallization
   "the hardening of concrete"; "he tested the set of the glue"
   hardening  solidifying  solidification  set  curing 
   
2. the act of making something harder (firmer or tighter or more compact)
   hardening 
   
3. abnormal hardening or thickening of tissue
   hardening