The act by which a person having authority, calls back or annuls a power, gift, or benefit, which had been bestowed upon another. Revocations are expressed or implied. An express revocation of a will must be as formal as the will itself. But this is not the rule in all the states.
Implied revocations take place, by marriage and birth of a child, by the English law.
In Pennsylvania, marriage or birth of a child, is a revocation as to them. An alienation of the estate by the devisor has the same effect of revoking a will. Revocation of wills may be effected, 1. By cancellation or obliteration. By a subsequent testamentary disposition.