"someone altogether different" is a correct and usable phrase in written English.
It means someone who is completely or entirely different from others. Example: After the accident, she came back as someone altogether different, with a new outlook on life and a determination to make a positive change in the world.
For those who watched "High Society" a year ago, however, Ms. Rose came off as someone altogether different: a villainous schemer.
When asked which candidate they would most likely vote for, most said they did not know or named someone altogether different: Mayor Giuliani, Gov. George E. Pataki, even the retiring incumbent, Daniel Patrick Moynihan.
Can't we intend to refer to something and end up referring to something or someone altogether different?[22] If our brains are just big lumps of electric jelly, presumably, our intentions must be found somewhere inside those lumps.
Someone completely different".
I have been dying to do this for some time but thought an altogether different person -- someone less clumsy -- was the sort to scrape out pumpkins, stuff them and bake them.
Yes, editing is a talent, but the ability to sit down and connect with someone through their work is something altogether different.
When Officer Martin took the stand in that trial, Mr. Greenberg confronted him, asking, "Didn't you commit perjury a week ago when you said in this very building, in an altogether different case, that someone had a gun in his waist?" The officer denied that he had lied.
Mr. Ebert's struggle with cancer gave him an altogether different public image — as someone who refused to surrender to illness.
But, he said, holding someone legally accountable for another's suicide was altogether different.
Or he goes on doing his thing, but someone at the side of the stage does something altogether different.
There is, however, an altogether different argument for these taxes: that when someone consumes such goods, he does impose a negative externality — on the future version of himself.
