What is the context? 정말 can be used in many different ways. If it is used as a noun, it means 'a truth' and has synonyms like 사실, 진실, 진짜. I'd say 정말 or 진짜 is less formal than 사실 or 진실. If it is used as an adverb, it means 'really' and its synonym is 진짜(로). Another use of this word is to stress on a certain emotion. e.g. 아 정말 왜 그러는 거야? = Argggg, why are you acting like this? Possibly, there are other usages of this word.

u can say "jinzaa" in oral because my system can not typing korean i wanna tell u .u can typing followoing letters W L S shift+W K ^ ^