Concise Bible Dictionary:
The word is ἄνομος, and is translated “without law” in 1 Corinthians 9:21; it is applied to those who, regardless of all law, do their own will (Acts 2:23 Thess. 2:8; 1 Tim. 1:9; 2 Pet. 2:8). It is wrongly translated “transgressor” in the AV of Mark 15:28 and Luke 22:37. A kindred word is translated “transgression of the law” in 1 John 3:4, which as a definition of sin is a serious error: it should be “sin is lawlessness,” and this term is equally applicable to those who never had the law.