I suppose implicating irrumatio to fellatio could also work practically, but I don't think it's technically accurate.
From the Fellatio wikipedia article:
Fellatio (also known as fellation, and colloquially blowjob, BJ, giving head, or sucking off) is an oral sex act (involving the use of the mouth, including the lips, tongue or throat) that is performed by one person on the penis of another person or oneself (autofellatio). Oral sex performed on a female is called cunnilingus.
From the Irrumatio wikipedia article:
"Latin erotic terminology actually distinguishes two acts. First, fellation, in which the man’s penis is orally excited by the [fellator]. Second, irrumation, in which the man (the irrumator)...engages in motions by moving his hips and body in a rhythm of his own choice".
That makes it sound like for it to count as "fellatio", the person whose mouth is in use has to be performing the movement, and that fellatio and irrumatio are two separate things.
Instead, I found on wikipedia: "The English noun irrumatio or irrumation and verb irrumate come from the Latin irrumare, to force one to perform fellatio."
That may be the etymology from thousands of years ago, but it doesn't necessarily mean it's still what it means today.
Edit: Since topic #9784 was locked in favor of this thread, I'll mention it again here:
create implication irrumatio -> oral