n.1 the act or an instance of invoking, esp. in prayer.
2 an appeal to a supernatural being or beings, e.g. the Muses, for psychological or spiritual inspiration.
3 Eccl. the words 'In the name of the Father' etc. used as the preface to a sermon etc.
Derivatives:
invocatory adj.
Etymology: ME f. OF f. L invocatio -onis (as INVOKE)