To reduce to a state of non-existance. To remove all trace of. Destruction in its ultimate form.

I annihilated that mysterious butt itch with one scratch.

Kill, destroy, obliterate, decimate, eradicate, smash, crush, beat the living shit out of... all good examples of annihilation, must I say more?

What I will do to you if you don't go away.

what the lord did to egypt... antibody-anni nile(river) hi-high late as dead(annile-hi-late)!?

Moses(mo says) used plagues to annihilate egypt.