on-sea•sonPronunciation: (on'sē'zun, ôn'-), [key]
being a time of year that is the busiest or most popular for a specific activity; in season: on-season airfares.
in or during the busiest season: to travel on-season.
a time of year that is the busiest or most popular for a specific activity: We stayed at the resort in the on-season.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.