sesquicentennial

adjective

1. pertaining to or marking the completion of a period of 150 years.

noun

2. a 150th anniversary or its celebration.

adjective

1. of or relating to a period of 150 years

noun

2. a period or cycle of 150 years
3. a 150th anniversary or its celebration

adj.“pertaining to a century and a half,” 1878, from sesqui- + centennial. As a noun from 1880; first recorded reference is to Baltimore’s.