A small sleeve, especially one that is part of a woman's garment.
Sleevelets are often seen as delicate and feminine.
Examples:
The dress has pretty sleevelets.
She wore a blouse with lace sleevelets.
The sleevelets on her dress were white and lacy.
I like the sleevelets on that shirt.
Her sleevelets were the most beautiful I had ever seen.
The sleevelets on her dress were like wings.