Relating to the number seven or to the seventh in a series.
The word septimal is about the number seven or things that come in sevens.
Examples:
The septimal month is July.
The septimal day of the week is Saturday.
She likes to wear septimal colors like the rainbow.
The septimal child in the family is the youngest.
In the septimal book, the hero has seven adventures.
The septimal note in music is the seventh one.