/on"see"zeuhn, awn"-/ , adj.
1. being a time of year that is the busiest or most popular for a specific activity; in season: on-season airfares.
adv.
2. in or during the busiest season: to travel on-season.
n.
3. a time of year that is the busiest or most popular for a specific activity: We stayed at the resort in the on-season.
[ by analogy with OFF-SEASON ]