unbirthday
/ʌnˈbəːθdeɪ
/noun humorous
Any day except one’s birthday: [as modifier]: an unbirthday present...
- And Mrs Du Faur may have been the first and last person to celebrate ‘unbirthdays’.
- They can draw money out of 401 plans and IRAs to celebrate their unbirthdays or prepare for their big 60th bashes.
- Ahhh, but there are three hundred and sixty four unbirthdays!
Origin
1871: coined by Lewis Carroll in Through the Looking Glass.