A sunfish.
"The biologist studied the behavior of sunny fish in their natural habitat."
Featuring a lot of sunshine.
"The valley was sunny all day, making it perfect for a picnic."
In plain English: Sunny describes weather that has bright sunshine and no clouds blocking the sun's light.
"The weather was sunny and perfect for a picnic in the park."
sunny side up
"She ordered her eggs sunny side up at the diner."
A female given name
"Sunny is having her twenty-first birthday next week."
The word sunny comes directly from the Old English term for "sunny," which has remained essentially unchanged in meaning over time. It entered Middle English as sunni before evolving into its modern form.