1. season (period in which regulated games are played)
大会シーズンではない。It is not the tournament season.
2. season (division of the year)
もうすぐ秋のシーズンだ。Autumn is almost here.
3. season (of a TV show, etc.)
この間、出てるシーズンまとめて買ってきたんだ。The other day I bought all the seasons that are out so far.
4. season (for doing something, e.g. ski season, entrance examination season)
今年もバレンタインのシーズンがやってきた。The Valentine's season has arrived again this year.