expression
with a fixed stare; with set eyes
Describes a person's eyes when they are staring intensely, often with a cold, angry, or determined look. The expression is a fixed phrase; the verb 据わる means 'to be set' or 'to be steady'.
彼は目が据わって、怖かった。
He had a fixed stare and was scary.
怒っているのか、目が据わっている。
Maybe he's angry; his eyes are set.