A person's eyes (and frequently hence expression or appearance generally), likened to a puppy's, especially in appearing mournful, beseeching, or winsome, or in eliciting (or being intended to elicit) sympathy or compassion.
Origin
1940s; earliest use found in Walla Walla Union-Bulletin.
Definition of puppy-dog eyes in US English:
puppy-dog eyes
noun
A person's eyes (and frequently hence expression or appearance generally), likened to a puppy's, especially in appearing mournful, beseeching, or winsome, or in eliciting (or being intended to elicit) sympathy or compassion.
Origin
1940s; earliest use found in Walla Walla Union-Bulletin.