Happening every two years.
Lasting for two years.
A plant that requires two years to complete its life-cycle, germinating and growing in its first year, then producing its flowers and fruit in its second year, after which it usually dies.
An event that happens every two years.
Occurring every hour.
Unsalaried, paid by the hour; (by extension) blue-collar.
At intervals of an hour.
Something produced each hour.