1 call on (a deity etc.) in prayer or as a witness.
2 appeal to (the law, a person's authority, etc.).
3 summon (a spirit) by charms.
4 ask earnestly for (vengeance, help, etc.).
Derivatives:
invocable adj. invoker n.
Etymology: F invoquer f. L invocare (as IN-(2), vocare call)
Useful english dictionary. 2012.