1. Occurring every third year or lasting 3 years

1. The 300th anniversary (or the celebration of it)
   - tercentennial, tercentenary

Derived forms: triennials

See also: periodic, periodical

Type of: anniversary, day of remembrance

Encyclopedia: Triennial

• back
• back and forth
• back away
• back bacon
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• back of Bourke
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• back-alley