From Longman Dictionary of Contemporary Englishopen seasonˈopen ˌseason noun [singular, uncountable] 1 DSO British English the time each year when it is legal to kill particular animals, birds, or fish as a sport OPP close seasonopen season for the open season for deer2 → open season (on somebody)
Examples from the Corpus
open season• There would be an open season on scattered singletons.• It is open season for criticising UDCs for lack of planning, lack of strategic thinking and short termism.• The grin meant it was open season. 