subnormal vs unstable

subnormal

adj
  • denormal 

  • Less than normal. 

noun
  • A person whose abilities are less than normal. 

  • That part of the axis of a curved line which is intercepted between the ordinate and the normal. 

unstable

adj
  • Unpredictable. 

  • Readily decomposable. 

  • Not stable. 

  • Radioactive, especially with a short half-life. 

  • Fickle. 

  • Having a strong tendency to change. 

  • Fluctuating; not constant. 

verb
  • To release (an animal) from a stable. 

How often have the words subnormal and unstable occurred in a corpus of books? (source: Google Ngram Viewer )