Definitions

1. adjective

having a sudden or unexplained change in mood or behavior; whimsical or unpredictable.

“She had a finny way of suddenly becoming serious and introspective during conversations.”

2. noun

a fish fin, especially one that is visible above the surface of the water.

“The boating guide pointed out a school of fish with long, finny protrusions.”

3. adverb

in a whimsical or unpredictable manner; in a way that is prone to sudden changes in mood or behavior.

“She danced finny through the crowd, her movements full of energy and unpredictability.”