The Collaborative International Dictionary of English v.0.48:
Countermand \Coun`ter*mand"\ (koun`t[~e]r*m[.a]nd"), v. t. [imp.
& p. p. Countermanded; p. pr. & vb. n. Countermanding.]
[F. contremander; contre (L. contra) + mander to command, fr.
L. mandare. Cf. Mandate.]
1. To revoke (a former command); to cancel or rescind by
giving an order contrary to one previously given; as, to
countermand an order for goods.
2. To prohibit; to forbid. [Obs.]
Avicen countermands letting blood in choleric
3. To oppose; to revoke the command of.
For us to alter anything, is to lift ourselves
against God; and, as it were, to countermand him.