ˈopen ˌseason BrE AmE noun [singular, uncountable]
1 . British English the time each year when it is legal to kill particular animals, birds, or fish as a sport OPP close season
open season for
the open season for deer
2 . open season (on somebody) a time when a lot of people criticize someone, or a group of people:
It seems to be open season on politicians just now.