This is the 11668th most frequent Russian word.
жирную
"Fatty" or "greasy" (feminine form in accusative case).
Here, 'жирную' is a form of the adjective 'жирный,' used in the feminine singular accusative case modifying 'свинину' (pork), to describe its quality as fatty or containing fat.
Она заказала жирную свинину на ужин.
She ordered fatty pork for dinner.
In this sentence, 'жирную' describes 'строку' (line), referring to its typographical style as bold, using the same adjectival case and number agreement.
Он написал жирную строку в тексте.
He wrote a bold line in the text.
Here, 'жирную' refers to 'мышь' (mouse), again illustrating the adjective 'жирный' in the feminine singular accusative case, used to describe the mouse as plump or fat.