A force or influence in The Free Dictionary.
The seventh item down in Google with search title Vector Verb Definition (just Vector verb gives you vector used as a verb no help) give Light Verb. Going to the article, you see that Vector Verb is another term for Light Verb. The article is found in Wikipedia.
In Urdu studies, the term Vector Verbs is used for exactly what Light Verbs are defined as: verbs whose meaning diachronically has been “bleached” to the point they are grammaticalized to indicate aspect rather than a lexical meaning. “Sit” in Urdu is used with another verb to indicate a violent action. So vw pani phayl baytha would be he spread the water around violently. (NB I need to check this paragraph)
So the Free Dictionary definition is the only one I checked with a definition that would help someone figuring out what vector verb refers to in Indo-Iranian languages, but not much. The Wikipedia article gives examples. The Free Dictionary does not even give a linguistic context and other definitions refer only to math, physics, biology, etc.