1. Size: The opposite of full lips in terms of size would be thin lips.
2. Shape: There isn't a single opposite for shape. Lips can be many different shapes, and what's considered "opposite" would depend on the specific shape you're comparing to.
3. Appearance: The opposite of "full lips" could be thin and flat lips, lips with little definition, or lips that lack fullness and appear sunken in.
Ultimately, the opposite of "full lips" is subjective and depends on the specific context.