see NY Times article (a ‘teritoepiest painter’ capable of rendering a picture in under two minutes of a subject mentally chosen by a spectator) or another handbill

these are the onliest online ref's we can find. the word is probably just broadside hyperbole and naught else. the only "help" I get from Lewis & Short is the Latin tero (teritur), to rub. [cf triturate]