bas ‧ ti ‧ on /ˈbæstiən $ -tʃ ə n/ BrE AmE noun [countable]
[ Date: 1500-1600 ; Language: French ; Origin: bastille 'strong building, castle' , from Old Provençal bastida , from bastir 'to build' ]
1 . something that protects a way of life, principle etc that seems likely to change or end completely
bastion of
These clubs are the last bastions of male privilege.
2 . a place where a country or army has strong military defences:
Pearl Harbor was the principal American bastion in the Pacific.
3 . technical a part of a castle wall that sticks out from the rest