What is Falsi Crimen?

Legal Definition
Fraudulent subornation or concealment, with design to darken or hide the truth, and make things appear otherwise than they are. It is committed

(1) by words, as when a witness swears falsely;

(2) by writing, as when a person antedates a contract;

(3) by deed, as selling by false weights and measures. Wharton. See Crimen Falsi.
-- Black's Law Dictionary
Legal Definition
The crime of fraud, defrauding by concealment or falsifying; forgery.
-- Ballentine's Law Dictionary