A "small smile" can be described using various words and phrases that convey the idea of a slight or subtle expression of happiness or amusement. Here are some words that mean a "small smile":
Grin: A broad smile or a smile with a closed mouth, often indicating amusement or satisfaction.
Smirk: A self-satisfied or smug smile, often one that is small and barely noticeable.
Nod and smile: A subtle smile often accompanied by a nod of acknowledgment or agreement.
Simper: A smile that is modest, often with one corner of the mouth slightly turned up.
Slight smile: A simple way of expressing a small smile without being overly descriptive.
Twinkle in the eye: A phrase that suggests a small smile or amusement reflected in someone's eyes.
Smirkle: A combination of "smirk" and "twinkle," suggesting a small, knowing smile.
Half-smile: A smile that only slightly lifts one side of the mouth.
Quirk of the lips: A slight movement of the lips that hints at a smile.
Upturned corners of the mouth: Describes the ends of the mouth turning upward, indicating a small smile.
Remember that language is flexible, and you can use a variety of words and descriptions to convey the subtleties of a "small smile." The context and tone of the situation can also influence how you describe it.