Bicentennial/ˌbaɪsenˈteniəl/ Definition 1 of 2Pro Tip 1/3Historical Milestone Used to mark significant historical occasions or anniversaries. The city's bicentennial parade commemorated its 200-year history. Pro Tip 2/3Not Annual Bicentennial is not an annual event, it occurs once every 200 years. Next year is the 199th anniversary, so it's not a bicentennial. Pro Tip 3/3Nation Celebrations Often involves national festivities and public holidays. In 2026, America will observe the bicentennial of its 50th state.