This is the 5044th most frequent Turkish word.
gözleri
"Eyes" (plural form).
Here, 'gözleri' means 'her/his/their eyes' and is used as a possessive form referring to the girl's eyes.
Gözleri mavi olan kız çok güzeldi.
The girl whose eyes are blue was very beautiful.
In this sentence, 'gözleri' refers to 'my father's eyes' and metaphorically implies the expression of joy through his eyes.
Babamın gözleri hep güler.
My father's eyes always smile.
Here, 'gözleriyle' ('with his/her eyes') uses the instrumental case of 'gözleri', indicating the means by which the action was performed.