Webster's Revised Unabridged Dictionary · 1913

Felon

Felon , noun

[Old English, adj., cruel, n., villain, ruffian, traitor, whitlow, French félon traitor, in Old French also, villain, from Late Latin felo. See Fell, a.]

1.
(Law) A person who has committed a felony.
2.
A person guilty or capable of heinous crime.
3.
(Medicine) A kind of whitlow; a painful imflammation of the periosteum of a finger, usually of the last joint.

Felon , adjective

Characteristic of a felon; malignant; fierce; malicious; cruel; traitorous; disloyal.
Vain shows of love to vail his felon hate. — Pope