Short slang term, for the obvious, a blow job.
Refers to oral masturbation. That is the ejaculation of a person, orally. Can be done by one's own self, if they are able to configure their body in such as a manner, as to actually insert their own penis, into their mouth.
In most instances, applies to a male being the primary receiver of the act, in straight circles.
Pre Christian Rome considered blow jobs, shameful, as it meant a male was being penetrated, controlled, thus not worthy of a Roman Citizen.
However, that did not apply if the subject doing the sucking, was a slave, or of a lower stature, in the social scale.