Longman Dictionary of Contemporary English
alpha male
noun
EXAMPLES FROM CORPUS
▪ They were also friendlier towards female infants and those not fathered by the current alpha male.
▪ You see it in nonhuman primates, where the new alpha male comes into the troop and mates.
Wiktionary
alpha male
n. 1 The dominant male in a group of animals. 2 A large and muscular dominating, controlling, protecting, successful, and leading man