This website contains age-restricted materials including nudity and explicit depictions of sexual activity.
By entering, you affirm that you are at least 18 years of age or the age of majority in the jurisdiction you are accessing the website from and you consent to viewing sexually explicit content.
This is seasonality.
To make it more generic, drop the “over a year” and just refer to the periodic signal over time idea. You can find additional signals by how you bin the data, eg monthly or day of week.
Seasonality specifically refers to periodic signals over the course of a year. Any other interval means it’s not seasonality. You can read that yourself in the definition you quoted.
I do this for a living. Seasonality as a generic term refers to temporally periodic signals but can even be extended to talk about non-temporal aspects of a signal. The same math used in areas like econometrics to remove periodicity in annual data can be applied to multiple domains. The main motivation to removing or isolating periodicity is to allow for investigation into the underlying phenomena, or to allow the investigation of the sources of periodicity independently of other drivers. In every case, though, seasonality is an acceptable term in everything I’ve written, read, and worked on.