deaf: unable to hear
At its plainest the word names a person who cannot hear. Scripture uses it that way to describe and protect real deaf people: the law forbids cursing someone who cannot hear the insult (Leviticus 19:14), and God reminds Moses that he himself is the one who makes a person deaf or hearing (Exodus 4:11). It travels in the company of two other words for physical limitation, the blind (עִוֵּר) and the mute (אִלֵּם), which the text repeatedly lists alongside it.
The prophet Isaiah then stretches the same word into a picture of the people of God. Israel has working ears but will not listen, so the prophet can call the nation itself "deaf" in the very breath that commands it to hear. The deafness here is not a broken ear but a closed heart, a refusal to take in what God is saying.
The two uses meet in Isaiah's vision of restoration, where the deaf hear again as a sign that God is putting the world right, and in the poets, who work the image both ways: a sufferer plays deaf to his enemies' taunts, while the wicked are as deaf as a snake that will not heed the charmer. The English word "deaf" carries all of this the same way, so the challenge is never the word itself but telling, verse by verse, whether a real ear or a hard heart is in view.