or  es*trum  or chiefly Brit  oes*trus  or  oes*trum  n 1 a  :  a regularly recurrent state of sexual excitability during which the female of most mammals will accept the male and is capable of conceiving  :  HEAT  b  :  a single occurrence of this state  2  :  ESTROUS CYCLE .
 
 
 
Similar sounding terms:  es·ter·ase  es·trous 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.