1. putting a person to death by mob action without due process of law;
The Collaborative International Dictionary of English v.0.48:
Lynch \Lynch\, v. t. [imp. & p. p. Lynched; p. pr. & vb. n.
Lynching.] [See Note under Lynch law.]
To inflict punishment upon, especially death, without the
forms of law, as when a mob captures and hangs a suspected
person. See Lynch law.
WordNet (r) 3.0 (2006):
n 1: putting a person to death by mob action without due process