idiomatopoeia
Various grunts, groans, growls, bawls, squeaks, squawks, hisses, purrs, boops, whoops, whizzes, whams, bams, pops, peeps, howls, churtles, chortles, gurgles, babbles, buzzes, and other verbalizations apparently reproducing a sound quality of a referenced thing and appearing to comprise meaningful articulations, but which, in reality, are merely the mindless noises of a complete idiot.
"No class," expressed the 7th grade teacher, Ms. Buzby, when Jeremy makes the "raspberry" sound, it's not a rude example of onomatopoeia, it's straight up idiomatopoeia.