"Give someone what for" is a common idiom that means to reprimand or scold someone sternly. Synonyms for this phrase include admonish, chastise, rebuke, reprove, scold, lecture, upbraid, or dress down. These words share the same tone and connotation, implying a forceful and serious reprimand. Other similar expressions that can be used in place of "give someone what for" include talking to, putting someone on notice, reading someone the riot act, or calling out. Whatever the phrase chosen, it is important to use good judgment in conveying the necessary seriousness of the situation while still showing respect for the individual being addressed.