Though derived from 'imperial' + 'orgasm', it has come to signify the subjection to a more animalistic or butchering rage which purges itself in an immense outburst of sexual desire or frustration.
B: "Fuck off, or i'll give you a fucking imperiasm!"
A: "Have you heard of a band called Meshuggah?"
B: "Yes! They are fucking imperiasmic!"