noun

unintelligible or meaningless speech or writing; nonsense.

he talks gibberish

nonsense,balderdash,blather,blether,rubbish,drivel,gobbledygook,mumbo jumbo,tripe,hogwash,baloney,bilge,bosh,bull,bunk,guff,eyewash,piffle,twaddle,poppycock,phooey,hooey,malarkey,dribble,rot,cobblers,codswallop,tosh,cack,cock,stuff and nonsense,double Dutch,havers,garbage,flapdoodle,blathers,wack,bushwa,applesauce,bunkum,tommyrot,cod,gammon,toffee,shit,bullshit,horseshit,crap,bollocks,balls,crapola,bulldust