Concise Bible Dictionary:
Used metaphorically to describe the state of man by nature under the influence of Satan (2 Cor. 4:4); also a professing Christian who hates his brother (1 John 2:11); also the state of Israel in their heartless profession (Matt. 23:16-26); and the judicial blindness on Israel (John 12:40). In Romans 11:7,25; 2 Corinthians 3:14 and Ephesians 4:18, it is rather “obdurateness or hardness,” from πωρόω “to harden.”
Strong’s Dictionary of Greek Words:
Meaning:
from, 5187; opaque (as if smoky), i.e. (by analogy) blind (physically or mentally)