What does it mean?

In American law, Scots law and under the law of some English-speaking Commonwealth nations, subornation of perjury is the crime of persuading a person to commit perjury, the swearing of a false oath to tell the truth in a legal proceeding, whether spoken or written. Wikipedia

verb. [with object] Bribe or otherwise induce (someone) to commit an unlawful act such as perjury. 'he was accused of conspiring to suborn witnesses'
suborn | Definition of suborn in English by Oxford Dictionaries
https://en.oxforddictionaries.com/definition/suborn