*bettor*

{ } n. One who abets; an instigator of an offense or an offender. [ 1913 Webster ]

☞ The form abettor is the legal term and also in general use. [ 1913 Webster ]

Syn. -- Abettor, Accessory, Accomplice. These words denote different degrees of complicity in some deed or crime. An abettor is one who incites or encourages to the act, without sharing in its performance. An accessory supposes a principal offender. One who is neither the chief actor in an offense, nor present at its performance, but accedes to or becomes involved in its guilt, either by some previous or subsequent act, as of instigating, encouraging, aiding, or concealing, etc., is an accessory. An accomplice is one who participates in the commission of an offense, whether as principal or accessory. Thus in treason, there are no abettors or accessories, but all are held to be principals or accomplices. [ 1913 Webster ]