testosterone

Etymology

From test(is) + -o- + -sterone (“steroid hormone”).

noun

1. (biochemistry, steroids) A steroid hormone that stimulates development of male secondary sexual characteristics, produced mainly in the testes, but also in the ovaries and adrenal cortex.
   Mammalian testes contain almost no testosterone because it is sent out into the body as quickly as it is made. 2019, Bill Bryson, The Body: A Guide for Occupants, Black Swan (2020), page 168
2. (figurative) Manly behavior, often of an aggressive or foolishly reckless nature.
   Mother encouraged James to rely more on intelligence and less on testosterone to deal with the neighbor's son.