Asperity

Origin

From Old French asprete, from Latin asperitatem, from asper ("rough").

Full definition of asperity

Noun

1. Roughness as of stone or weather.asperity of Maine's winter
2. Harshness, as of temper.
• 1878: W. S. Gilbert, :Go, ribald, get you hence
  To your cabin with celerity.
  This is the consequence
  Of ill-advised asperity!
3. Something that is harsh and difficult to endure.
4. (geology) A part of a geological fault line that does not move.Earthquakes begin and end at asperities.