1. (adjective) Small in size; tiny; little. This is the most common meaning.
* Example: "She wore a diminutive hat on her head."
2. (noun) A word that expresses smallness or endearment.
* Example: "Honey" is a diminutive of "honeybee".
* Examples: "Little", "Tiny", "Mini", "ette" (as in "kitchenette")
In essence, something diminutive is small or suggests smallness, whether in size or in a more metaphorical sense.