Definition of capsaicin in English:
 capsaicin
noun kapˈseɪɪsɪnkapˈsāəsən
mass nounChemistry A compound that is responsible for the pungency of capsicums.
A cyclic amide; chemical formula: C₁₈H₂₇NO₃
 Example sentencesExamples
-  What was known was that certain types of nerve endings responded to capsaicin by allowing calcium ions to flow into the cell.
 -  In the fight to protect both elephants and humans, the chemical agent capsaicin, found in chili peppers, is a secret weapon.
 -  Chillies are ‘hot’ because they contain capsaicin, an irritant alkaloid which is found mainly in the interior tissue to which the seeds adhere.
 -  What you were up against was the awesome power of a chemical known as capsaicin, an odorless, flavorless substance present in chili peppers.
 -  Although capsaicin causes respiratory problems, the researchers did not find evidence of any unique metabolites in lung microsomes.
 
Origin
  
Late 19th century: alteration of capsicine, the name of a substance formerly thought to have the same property.