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definitions

on-season

[on-see-zuh n, awn-]
adjective
  1. being a time of year that is the busiest or most popular for a specific activity; in season: on-season airfares.
adverb
  1. in or during the busiest season: to travel on-season.
noun
  1. a time of year that is the busiest or most popular for a specific activity: We stayed at the resort in the on-season.

Origin of on-season

by analogy with off-season
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018