A felony is a serious criminal offense punishable by imprisonment for more than one year or by death.
Merriam-Webster Online Dictionary
felony (noun)1.
an act on the part of a feudal vassal involving the forfeiture of his fee
2.
a) a grave crime formerly differing from a misdemeanor under English common law by involving forfeiture in addition to any other punishment
b) a grave crime declared to be a felony by the common law or by statute regardless of the punishment actually imposed
c) a crime declared a felony by statute because of the punishment imposed
d) a crime for which the punishment in federal law may be death or imprisonment for more than one year